Why do I keep getting a loop when knitting? I'm learning to knit and I can cast on just fine. I can also knit stitch quite well. I have not learned the purl stitch yet as I cannot figure out what I am doing wrong. Whenever I knit stitch, the last stitch always has a big loop in it that I cannot remove. I've tried pulling from all different places but the loop stays there. One time i thought I fixed it, but I ended up with 11 stitches when I started with 10.

From what you are saying it sounds like you are getting a loop at the end of your run of knit stitches when you go to purl stitch.  If this is the case, I have experimented to confirm the cause and believe you are not bringing the yarn around the needle to the front before you purl.

Do not bring the yarn over your needle.  This could possibly be why you are also getting an extra stitch (11 stitches instead of 10).  It needs to go around it to the front (bring it in between the 2 needles to get it to the front). Knit stitch has the yarn at the back, and purl stitch has the yarn at the front.


Learning to work with a rotary tool More or less by occasion as I searched for something original I could craft myself, I decided to craft a walnut jewelry box for the proposal. It went well! :-)

For this purpose I had bought a rotary tool accompanied with a set of drill and sandpaper bits.

Now I ask myself how to explore and study more what I could do with this rotary tool but in a more systematic way than jumping from one YT tutorial to another.

I like the wording from the Arts&Crafts movement regarding exposing the natural beauty of materials. While I am not a great artist, I think I could learn to craft more or less simple things.

Local makers DIY shop has more electronics/hardware background than arts and crafts. Maybe there is a good entry level book to start with?

You've got a local makers DIY shop, so that is probably your best bet.
If it's current membership don't focus on crafts, just ask the leadership if you can start a craft night.  Volunteer to teach people how to make that walnut jewelry box during the first meeting.  Then at the end of the meeting, ask for other presenters to teach on other craft subjects.  With a little luck, you could build a thriving craft community very quickly.  Somewhere in that growing community, you will find the rotary tool teacher who can help you master it in an orderly fashion.

Beyond that, the best way to master a tool is to use it.
Find tasks which need doing where your rotary tool can play a part.  Then research on YT how to apply the rotary tool to that task.  Each new task completed increases your skill with the tool and in a surprisingly short time, you will have more new tricks to teach to your growing craft community.


Is there a name for an orange, gray and white -style pattern? I've heard somewhere that an orange, gray and white "style" has a specific name. I believe that it has "minimalism" in it, but I cannot recall.

Here is an example of the color scheme, but in my case it's more about user interfaces design in software, corporate logo style, corporate branding and so on.

Is there an actual name for this style?

Based on the images you've shown, where the main colors are the shades of grey, I'd call it grayscale with a single accent color, in this specific case, the accent color is orange.

You could also call it black and white with a single accent color but that might lead people to believe that only black and white were used rather than shades of gray.

Something similar can be seen in these ceramic items:

If you were talking more about something like this tea kettle:

It would be the opposite - orange with grayscale accents.

If you're using multiple shades of the same orange (same color, different amounts of white/black), it would be "monochromatic", like the image below, which is an underpainting of a finished painting:


How can I stop dye from rubbing off burlap? I recently acquired some burgundy burlap to use in re-upholstering some straight backed chairs. Problem is,  the color comes off if you rub hard against it (like sitting down!). Any suggestions on how I can set the dye job on this material? Returning it isn't an option.

Thanks,
Jackie

It is hard to guess what went wrong in the dying process, but I am assuming you have a natural jute fiber burlap. You will probably have to dye the fabric again. What usually works is Rit - which you can get at pretty much a y fabric store. Be careful, it is a little caustic and will stain your skin.

If you want to try to fix the dye, don’t use salt or vinegar - caustic soda might work, but you probably want to get retayne as it is described here. Apparently also available at quilting and fabric stores, I must say that I do not know the product but the science seems sound.


Replenish the ink of a fountain pen by dipping Will a fountain pen suck up the ink into its reservoir if I simply dip its nib into the ink?

If the fountain pen has any kind of (suction) pump, then you will need to use the said pump.

The capillary effects alone will not have the power to fight the weight of the ink itself.

My personal hack

I have a fountain pen with one-time-use cartridges. It came originally with a very long one (compared with what is usual in shops). Because I did not want to purchase so much plastic (the small one time use cartridges), I decided to use the original one. To refill it I use a syringe (dedicated specifically to this purpose) to transfer ink from the ink bottle to the cartridge. I use it in this way for more than 20 years without any issue. The original cartridge, even though it was designed to be one-time-use, still fits properly, without leakage, to the pen.


How to utilise plastic straws? I want craft ideas because I have a heap of plastic straws that I want to use for some sort of craft. Any ideas?

If you also have some thread and a long needle, you could jump into exploring geometrical shapes:

To build them, thread three straws (or parts of them) and tie them together to build a triangle. Then add further triangles at the edges.


Materials and procedures for painting acrylic (Plexiglass) sheet I would like to paint acrylic sheet (Plexiglass) with acrylic paint.  Both the sheet and the paint are opaque (black or white); single color all over.

What kinds of paint should I use? What kinds of paint should I avoid?
Are all acrylic paints created equal? My local home improvement store
carries acrylic paint, and they can make a variety of colors on the
spot; would that paint work?
How to prepare surface? Do I need to apply primer first?  If so, what
kind of primer?
What can I use as varnish on top of the paint?

To put this question into perspective, painting is only the 1st stage of the process.  In the 2nd stage, I will burn off the paint with a laser.  So, if I've got black acrylic with white paint, and I ablate the paint selectively, then I will have black details on white background.  (This is not unlike LaserMax sheets.)

I know how to do the laser.  I don't know how to do the paint.

As long as the underlying panel will not flex, yes, you can use normal acrylic paints, but a primer is required, and the recommended method is to fine sand the plexiglass to a slight roughness, then cover with primer.

Acrylic polymer varnish is ideally suited to varnishing over acrylic paint, and I'm pretty certain you can use other varnishes.


Embedding a neodymium magnet inside a forged/melted aluminum enclosure I want to embed a rare earth magnet inside some aluminum. Think of it like an aluminum rod that has a thin layer of Al at one end, and underneath is the rare earth magnet.

Al melts at 660C. At what temp does neodymium melt at? Is there a magnetic material that has a higher melting point that I can embed in the Al?

The melting temperature of a magnet is irrelevant because it loses it's magnetation long before melting.

Have a look at this site and you'll see that the maximum working temperature of neodymium magnets is approx. 230°C for the most heat resistant magnets. This site explains why the magnets get permanently demagnetized by heat.

The only way to embed a magnet into aluminum and keep it intact is to prepare a cavity in the aluminum and insert the magnet later (when the metal cooled down to working temperature). If you want to coat the magnet, either use galvanization or a different material.


How can I cover my desk chair's seat? My desk chair has started peeling. I think the cat scratched it, and now more comes off after every seating.

Here's what the seat shape looks like:

After looking into this a bit more, I realized that only the top & front of the seat have this material (the four sections easily seen in the picture). The sides and back of the seat are vinyl. I don't know if this changes much.

I'd like to do something such as a fitted sheet, but I don't know how to go about measuring a pattern, especially if I plan on elastic edges. I'm also concerned about it sliding or becoming loose. The seat is concave. I don't want to sit on wrinkles.

Is there a better solution than a fitted sheet? I don't want something I need to adjust all the time.

I'm not asking for detailed instructions or total walk-throughs. I'm just not sure on what type of solution to use. Once I pick a solution, I'll ask specific questions if I get stuck.

You should be able to turn the chair over and unscrew the seat part. If the cover doesn't come off (probable), you'll need to trim the loose pieces and make patterns for each section. If you don't want wrinkles, you need to cut fabric out in the pattern of the original seat. You need to allow for seams and fold over the edge (measure the edge into the plate that screws the seat to the chair. An easier option without the pieces is to use a stretchy woven or a firm knit, but in time they will sag.
You can probably just use duct tape to attach the fabric under the seat plate.


I have a model with a latex allergy: what are my other options? I do amateur make up for a local theater group. We have a few of our actors and extras that have latex allergies. Generally I simply avoid using prosthetics on them since I do not have a good solution.
So what are good options for people that can not tolerate liquid latex?

If your models cannot be in contact with latex you can use alternatives. Since Latex comes in many forms it's not entirely clear which form you're using but I assume you're mainly referring to latex prosthetics.

Latex

I think the most common alternative would be to use silicone. Silicone is a man-made alternative to the more natural latex, and it generally ages better so silicone appliances can be stored and used later and will keep better than a latex appliance.

Liquid Latex

If you're looking for alternatives to liquid latex, you can use Elmer's Glue or spirit gum if you're using it as an adhesive.

I also found this cool site which shows you how to make a faux version of latex from home which considering your amateur nature may be appealing.

http://www.diypics.com/how-make-latex-fx-makeup/


Something against hand pain due to writing? I sometimes write for hours per day (calligraphy), and my hand starts hurting because of holding the pen for so long.

Is there a solution to this problem, e.g. some kind of glove or pen-strap that reduces pressure on the fingers?

If your hands start hurting or feeling sore, take a break. Listen to your body - if something hurts, it needs to rest. Otherwise, you can risk permanently injuring/disabling yourself. One artist whom I follow, Yuumei, has shared her experience with this: https://www.deviantart.com/yuumei/journal/PSA-for-Artists-Don-t-make-the-same-mistake-I-did-577426340. I personally will take breaks to stretch my hands and massage the sore parts of my fingers. If they're still hurting after a break, then it means I'm done for the day. It's not worth risking permanent disability by pushing yourself to draw/write for a few more hours.
Check your hand/wrist alignment when you're writing. I've found it helpful to rest my wrist on a rubber/foam coaster - it adjusts the angle of my wrist just enough to relieve some of the pressure.
Explore other methods of calligraphy. I used to draw extensively in pencil (graphic and colored pencil), but over time I found that the pressure created a lot of pain in my joints, especially where I held the pencil or rested my hand/fingers against the table. I started painting instead, which doesn't require much pressure to create a visible mark (and requires much less energy to fill a space with color). Perhaps try using a brush instead of a pen from time to time, and see if that provides an outlet for you to continue doing calligraphy without wearing your hands out as much.


knitting and crochet yarn gauge When shopping for yarn I noted numbers like: 50/6 or 34/6.  I am looking for a chart of similar numbers to understand the system.  Else, to know what these specific numbers mean.
Thanks

These numbers tell you the size of the yarn and how many plies it has. It's called the "count system".

The first number is the size - the larger the number, the finer the yarn. (The physical sizes can vary for different fiber types, but they always follow that rule.)

The second number is the ply, how many singles make up the yarn.

So both of your examples are six-ply yarns, but the 50/6 yarn will be finer than the 34/6.

If you spin yarn, these numbers will tell you how much fiber you need to make a certain length. Fibers have a count associated with them (also different for each fiber type - for instance, cotton is 840 but linen is 300). That number is how long a single ply of yarn would be, spun at size 1, if you used 1 lb of fiber. So 1 lb of a 1/1 cotton would be 840 yds long. However, if you wanted to make 10/2 cotton, you would multiply by the fraction: (10 / 2) * 840 or 4200 yds of yarn, from the same weight. This value (yards per pound) is called the "grist", and is directly correlated with the count system number.

Reference


What fabric would work well for a flag? I want to sew together a flag and I was wondering what type of fabric would be best to use. I'm looking for something opaque, thin, non-stretchy, and available in various colors. I initially thought cotton or fleece would be good, but cotton is too stretchy and fleece is too thick.

Most commercial flags are made out of nylon. It's lightweight, durable, and dyes well. Specifically, the flags on many sites are made from DuPont SolarMax™, which is supposed to be nicely color safe in the sun. For inside use, you should probably be fine with a ripstop style nylon.

  This heavyweight DuPont SolarMax™ nylon is the most popular and versatile flag fabric available. Nylon's combination of strength and brilliant display, along with its quick drying ability, make it suitable for a wide range of applications. Great in rainy areas, its light weight and close weave enable it to fly in the slightest of breeze, giving the fullest visual effect. Nearly every flag we sell is available in nylon material.

Other options include various types of polyester, which is unlikely to stretch the way the cotton you've been using has,rayon (which is a cellulosic fiber like cotton, but does not have the strength of cotton), and the right type of cotton, which is apparently a "2x2-ply mercerized cotton", which is specially prepared in such a way that it absorbs more dyes, is more lustrous, and stronger, so it is less likely to stretch or deform.


What is this handmade ceramic good for? We have bought this beautiful piece of ceramic.  We have no idea how it is supposed to be used beyond the obvious decorative purpose. Any idea?

It has an opening but we don't think it can be used as a salt (or pepper) shaker since the holes on the windows are too big and too close to the bottom.

It looks very much like a potpourri holder. It is certainly a lovely little piece. I would recommend that you look after it carefully, and make sure that it comes to no harm. The ceramicist appears to be Edith Rimington, of Flintshire, Wales, although I have not been able to find out anything about her on the Internet. This is a piece that may appreciate in value, but I would definitely keep it for its simple charm.

I think that we should avoid confusing Edith Rimington with the English surrealist artist, Edith Rimmington (1902 – 1986). I doubt if they are the same person.


Appropriate tool for measuring longer warps What's the best method for measuring out a three meter plus warp? I do make felt from my tail trimmings but I prefer to keep wool wastage to a minimum
On this occasion I'm doing a single colour warp with 160 pieces of wool. Tabby weaving on a ridged heddle.

For roughly 2m or shorter  I just use the back stick and a peg. Some of my concerns for using that method over a longer length is keeping the tension the same across each strand and I will have to take my loom to an art space to have enough space. I've used a mill once for an 8 shaft but i didn't like how little number you can put on. Would a board with custom length pegs be my best option?

Any time you dress your loom (put the warp threads on) via the indirect warping method (measure out your warp via a warping mill or board), you don't need to measure out all your warp threads together. If you are doing a project with 160 ends, you can use a warping mill or board to measure out two groups of 80 ends each, and put them on the loom one at a time. Here is a link to a YouTube video that shows a good way to store warp until you are ready to put it on your loom: https://www.youtube.com/watch?v=VQ1qNeSYBxs (You can also go to your favorite search engine and search for "how to warp chain" and find similar resources.)

A custom made warping board with extra long pegs sounds like it would be a great thing to have, but if you already have a mill or board, measuring out your warp in smaller groups is one way to make do.


Is there a cheaper alternative to aluminum wire for armatures? I've seen many sculpting tutorials and recordings of works where the artist uses aluminum wire for the armature, with aluminum foil used where bulk is needed for the form.

However, as a beginner, aluminum wire is too expensive for me to essentially waste on practice projects. I've tried steel wire, but the thicker gauges are practically unworkable. Almost every hobby and craft store I've been to only sells aluminum wire in the floral section, at very high prices per foot, and online stores sell much more than I need.

Is there a cheaper alternative aluminum? It doesn't need to be as flexible, but sturdy enough to hold the clay and be safe in the oven.

A couple of alternatives.

Firstly, cheap and cheerful, use metal clothes hangers (normally given free from the dry cleaners). However, this would only offer you a limited range of gauges.

Secondly, pop down to your local DIY/Garden Centre. They will have a large selection of fencing & plant growth materials. You will find all sorts of wire used for fixing trellises, plant growth leads, etc.

Final alternative is to strip out the copper conductor from old electrical cable.

  Make sure that the cable is disconnected from any electrical source

This will provide you with a selection of gauges depending on the conductor size. However, once you get above 4mm you find that the conductors aren't solid but in strands.

Of the above, the local DIY/Garden Centre will yield the best results.


Is it safe to use the tip of a hot glue gun to melt crayons? This video (https://www.youtube.com/watch?v=FV4hfmODq94) mentions the following methods to melt crayons:

Putting the crayons into the hot glue gun.
Using a hair dryer and point to the crayons.
Using a lighted candle and point to the crayons.

So, I was wondering if the following method can be a fourth method to melt crayons?

By using the tip of a hot glue gun to slowly melt a crayon.

Will that cause any damages to the hot glue gun?
And are there any precautions that I need to take note of?

It will work, as high temperatures melt the crayons, regardless of the device you use, but in all cases I'd suggest doing it in a well-ventilated room or outside, as the fumes are a little toxic.

Also note that holding the crayon in one hand while doing so is asking for trouble: wear a glove, or attach the crayon sturdily to something.

I'm sure crayons won't damage the glue gun more extremely than the glues it is used for (I mean, the tip of the hot glue gun is made to withstand damage).


How to paint rough but distinguishable people with oil paints? I've been teaching myself wet on wet expressionist style oil painting lately and my landscapes, cities look awesome. But...

But when I go to add some small detail in amongst the fray, particularly people and other non geometric objects, they end up blobs of mixed colour. With a knife, you can scrape a shape to clarify  confusing details, but small, complex objects are just hard... especially people.

If the colours didn't just merge with the background, people would be easy, but they don't obey me.

Bob Ross says use thinned paint to paint over the background, but this doesnt seem to work all that well for people :(

Edit:

As per request, here is one of my paintings. A small representation of an ancient city. I finished it dissatisfied that there were no people in amongst a city, and so wanted to add them to give some nice perspective, but never intended for them to take over. However, the first reaction my brother had was 'what is that?' - and I would agree. I wanted them to be dark blue to fit with the theme, but adding a dark blue figure (and her child) just blended straight into the wet background on the left, and thus in a last ditch effort I repainted the character on the left in grey with loads of thinned oil paint and tried to add small blotches of skin tone to the face in order to push the concept of a person. Nevertheless I am pretty displeased.

Because of her blobby she got, it became hard to give her a reasonable pose or make her look.. Good.

On the right a couple are (supposed) to be walking away from the audience, but really they are nondescript blobs. They fit in with the colours, but with no discernible features.

Perhaps I'm too picky.

There are a few things to consider, that I can think of at the moment:

This merging with the background and the blobs are actually the charm of the technique. You either learn to use it to your advantage or find a technique that serves your means better. (You can mix techniques, too, of course.)
Generally speaking, wet-on-wet works better on larger scale canvases because of the smudge-like nature of the technique.
For applying paint in detailed manner get a fine brush, either flat of pointed. The ones I'm referring to are actually not meant to be used for oil (I think) but they work fine with it (as long as they are not the ones with ultra-soft bristles; all brushes for oil need to be fairly stiff). You will still have some mearging with the background, though.
You can add fine details to your painting without the merging by letting the layer you've painted dry a bit and then paint on top (but this is not wet-on-wet).


Best material to make cardboard more durable I'm planning on making a cat wheel out of 48"-60" Sonotube.
How would one go about making a rigid paper-like material similar to cardboard more durable, i.e. resistant to spills, dents, and dings? There are many products on the market, e.g. polycrylic, flex seal, truck bed liner, various paints, etc... that I'm facing some analysis paralysis.

For your objective, spill-resistant and ding resistant, you're dealing with two parameters that could be combined. As noted in Bill Horvath's answer, the weight will be a factor.
Cardboard for concrete forms is pretty durable and somewhat moisture resistant "out of the box", and could take mild abuse without modification.
Virtually any paint will protect the material from moisture once cured. The biggest enemy of cardboard is water and other liquids. Paint will be lightweight, the lightest option, and likely the least expensive route. Even rattle-can paint can accomplish water protection and allow for artistic expression as well.
One step up from paint, providing protection and a minimal amount of ding suppression, would be a coating of water-resistant glue. I used "water-resistant", but some products explicitly state waterproof. One such product is Titebond III Ultimate Wood Glue, which uses those terms on the website. One would brush on several coats, allowing the previous coat to become tacky to avoid drips, runs, and spatters. Once fully cured, the glue becomes a force-distribution surface, spreading out any impacts. If the glue becomes damaged, it's an easy repair.
Other surface finishes which provide for water-repelling features would work, of course. Some finishes may not work for impact protection, while others (epoxy-based products) may be overkill.
Beyond this level, one will most certainly be adding weight. It's not absurd (but pretty close) to consider that a single layer of fiberglass with polyester resin could make a substantially strong cat hoop, but the weight comes into play again.
Polyester resin or epoxy resin of a thin consistency will provide waterproofing and not all that much weight while giving the durability you require. Additionally, using such a coating on the outside will improve the durability of the bearing contact areas. If applied on the inside surface, adding grit prior to curing gives the felines more confidence and less cartoon-cat skittering.


How can I make paper look old without wetting it? I want to make paper look aged and then print on it a picture, I tried with coffee but the results were bad, the picture quality is poor on the coffee paper compared with the white paper, the colors are really dull and it is less saturated. I tired to fix this with photoshop but nothing worked out, We don't have ivory/yellow/brown papers available in my country and I can't get it online too. I was thinking to buy maybe a fixative spray, I contacted all stores here, they don't sell it but they do sell a acrylic varnish mat spray, will that helps ? or I shouldn't be using an acrylic spray on an inkjet photo ? it'd be much appreciated if you guys can help me with an aging technique (it doesn't need to  appear really old or something) just a yellowish/brownish color. I don't want to wet the paper with coffee or tea or anything because I lose quality

If you're printing, why not print the aged effect as well?
Print it as close to the margins as possible - your printer may even do borderless, but if not you need to crop (physically) to the aged bit.  This doesn't have to be perfect; in fact it may be better done rather roughly, depending on just how old and weathered you're looking for.
If you do tea- or coffee-stain your paper, you need to dry it really well before printing, and get it really flat (e.g. iron it). This may make that an option after all.


Cut even circles out of felt We recently created a kid's activity out of felt. It's pretty neat... except for the circles. They're pretty uneven, with a lot of jagged edges or straight parts.

Is there a technique or tool that will help us create "perfect" circles out of the felt? A swivel blade with a plastic stencil works well on paper and thin fabric, but not so much with the thicker felt material.

You can try to use a compass cutter like this:

I find this product rather effective on materials like leather or felt. The only problem could be if your felt is too thin, in this case it could be too flexible and it could move around while you move the compass, but I have only had this problem when I tried to cut household linen.


A way to efficiently and effectively combine papers for musical scores I printed out some sheet music and would like to combine the pages. Currently I use tape and I cut the margins out (I need to just rescale the pages). The taping is kind of a pain because if things are not lined up it creates minor problems (it probably would be better to tape one page then lay the next one on the tape, but I am butting them together then taping). Of course both sides need to be taped, but one side is not sticky.
Not sure if there is a machine, device, or product that could be used for this that would work well? I do need it to fold for storage and probably plan on putting them in a binder when not in use. If there was a sort of dual end tape where the middle was not sticky then it would be pretty cool. It wouldn't solve many of the problems but would help with only having to tape one side.

I assume you need it to lie flat when open, and don't have access to a printer that will print double size pages (e.g. A3 if you normally use A4). If you do have such a printer it's easy - fold in half and use a long arm stapler or sewing machine in the crease.
A comb binding machine would work well, giving you a book that lies nicely open. You can add, remove, and rearrange pages, and there's no tape. There is a margin needed at the seam though, so if you're joining the pages to get very long lines (which I've never seen in sheet music) this won't work.
Otherwise you can stop the residual exposed surface of tape being sticky by dusting it with talc after you've made the join. This will just brush off the paper.


What can cut curve curved glass? Let's say you want to cut around a jar which is very curved, a traditional glass cutter wouldn't work well, so what would you use?

Specifically for cutting glass jars and bottles

A very common method is to use heat shock to break the glass; normally by putting a ring of some form of absorbent string or twine around it, soaking it in acetone or some other fuel, lighting it and then plunging the bottle into very cold water. Some tutorials recommend that you use a glass cutter just to score the surface lightly to increase the stress, so it seems that using a glass cutter might also be possible (if difficult).

For cutting arbitrary curved glass surfaces

Honestly, a traditional glass cutter or dremel is probably still your best bet. If you're struggling to hold it steady on the curved surface, consider covering it with masking tape to give the piece a more friction - this should make it easier to cut without slipping.


Can this origami figure actually be made? In The Arrival, by Shaun Tan, the protagonist makes origami, including this bird.

Can that figure actually be folded, as drawn? Or did the author just draw something vaguely origami-ish?

Looking at Robert J. Lang's Opus 822, Northern Mockingbird, it's entirely possible to create a base for a bird model that incorporates flaps for head, wings, tail, and legs.  How easy it might be to do without being Lang or knowing a technique to create a base with the appropriate flaps for those features (e.g., circle-packing), I don't know.


Epoxy: adding fresh over cured I have read in several places that adding fresh silicone over cured one will not work, as the new silicone will not adhere to the old.

The question is: if I create some object of epoxy resins, can I repair dents by adding more (fresh) epoxy?

In my experience fresh epoxy will bond with already cured resin just fine.

Both the cured and fresh epoxy should be the same chemicals. I have no experience with layering different types of resin.
Given that the surface of the cured resin is clean (no dust or oily residue) and both batches have the same color you cannot see the individual layers after the fresh resin cured.
Given the first batch of resin cured right (the resin to hardener ratio was right and it's not still soft or sticky) I was never able to seperate individual layers of resin without breaking the object. You cannot "fix" a batch of resin that doesn't cure because of wrong mixing ratios by pouring more resin on top. You can only stabilize slightly bendy resin.
If you expect the joint to come under tension, you should roughen the cured surface with coarse sandpaper. This gives the fresh resin a bigger surface to bond to but will become invisible if you remove the dust before pouring.
You should keep surface tension in mind. Pouring fresh resin over only part of a cured object creates a visible transition and the fresh surface will reflect light differently because surface tension pulls it into a different shape. I highly recomment covering the entire surface of a cured object with a thin layer of fresh resin to repair dents or holes. Pour enough resin that the surface tension cannot pull the fresh resin away from corners or high edges (happened to me several times)

When I craft with resin I often cover objects in several thin layers of epoxy. In videos you often see people grinding and polishing their epoxy jewelry to a shine in a long process. If you don't need perfectly even surfaces, you can pour a thin layer of epoxy on top instead and archive a finish that's clear and shiny without the trouble of polishing.


How would I flatten a watercolour mounted on mat board? We have a watercolour that was mounted to a piece of mat board by the artist (over 40 years ago) which needs its framing renewed. After pulling the backing off, I find the mat board is badly warped (part of the reason it needs renewal it turns out.) The mat in front (separating the work from the glass) seems to follow the backer.

Should I try to flatten the mounts or just make sure all is secure in the frame? (Or take it to a pro?)

So, first, I would probably take it to a professional restoration if there was no way I was willing to risk the painting. Likely to be expensive, though, but the safest approach.

If you want to try to flatten the support, you could try slowly wetting the back of matboard with sponged water, don't soak it, wet it, and then flatten under heavy pressure (carefully, you don't want to damage the painting) for a couple of days. This may bring the matboard back into shape, but it's a bit of a long shot really.

I have to be honest, though, if the work was one that I wanted to preserve, I'd be looking to a pro to do it.


How to fix the nose in this portrait of soft oil pastels? I paint with soft oil pastel on black canvas board.
Painting noses is difficult.
I feel the nose should be short, but it will increase the distance between the nose and the upper lip.
If I decrease the distance between nose and upper lip, it will make the nose too long. I tried to fatten the lip.
I'm totally stuck, does anyone have any advice?

To me the proportions look right. I think your problem is the contrast in color between the tip of the nose and the skin above the upper lip.

In your reference picture there is a very soft and gradual blend from nose to upper lip. The lightest color is on the very tip of the nose, where most of the light is reflected.  The parts of the nose that physically point downwards lie in a soft shadow. At the same time the nose casts a soft shadow onto the skin below. Both parts have a very similar color. It's impossible to see exactly where the nose ends and the skin above the lip starts.

In your painting you painted the shadow below the nose, but all parts of the nose are very bright. That creates a sharp contrast and your eye is drawn to that specific point. Your brain cannot stop analyzing this point because of the sharp edges.

If you darken the underside of the nose, this contrast dissappears and your eyes are drawn to the brightest spot - which is now the eyes. The human brain fills in the information that the eyes don't see clearly and suddenly the nose has exactly the length the observer likes best.

The same effect can be observed in the famous Mona Lisa. All the contours are so soft and blended that each observer sees the image a little different. If you look at her eyes, you cannot see the lips clearly and your brain automatically fills in the missing information with "she's smiling". If you look at her lips, you suddenly realize that she isn't actually smiling, there's just a soft shadow pointing upwards where the corners of her mouth would be if the was smiling.


How can I fix the "foxing" of a shoe? I left my shoes in my backyard, then somebody let the dog out and part of the shoe died (sad story). Now my parents are making me fix the shoe, is there any "replacement for the foxing?

The most realistic fix is to buy a new pair of shoes...
If you must fix this somehow, be aware from the very first second that it will never look new or professional again and will probably break again very quickly.
First you need to cut away all the losee strands and pieces. The heel could probably be repaired with construction silicone (preferably white). I suggest applying several thin layers and rebuilding and sculpting the heel that way. You can shape the fresh silicone with your fingers if you dip them into a glass of water with lots of dish washing liquid.
The upper edge is pretty much a lost course. You could try hiding the damage by sewing on a new bias tape, but since some material is chewed away, it will always look bumpy. I would be very careful when sewing through so many layers. The needle bight break. Maybe glueing the bias tape on is the better solution.
That being said, whether you try to fix them or not, you'll probably end up replacing them very soon anyways.


How to prepare and carry out drawing line art on a tree round? Our business is an outdoor children's nursery and we thought it'd be nice to make a sign with our logo on a large tree round rather than printed on plastic, since it better reflects the outdoor/natural ethos.
We have some trees that have been felled and another which is due - beech and sycamore - about 2 feet in diameter, and could get a round maybe 1-2" thick.
This is our logo (sorry only version I have to hand is small):

The thinking is this (maybe simplified) would be somehow 'etched' into the wood maybe 1/4" deep and 1/2" wide or so, then probably those lines would be painted so we get a colored line-art on wooden backdrop. Burning could be another option but I think we would still like the lines 'etched'
So the questions I have are:

how should wood be prepared in terms of drying and maybe treating?
How would the 'etching' be done? Is this a job for a router or something else?
Does this type of craft have a specific name I can read more about?

Preparation
As the wood dries, it shrinks.  You'll likely get big splits and cracks.  The rule of thumb for a board (vs. a round) is a year of drying per inch of thickness.  Wood dries faster through the end grain but also tends to develop splits and cracks as a result because of the uneven shrinkage (but has less tendency to warp in that orientation).
You can slow drying by sealing the end grain, but on a round, that leaves a lot of wood for water to migrate through, so drying could take years.  A round two feet in diameter is pretty big and limits some of the tricks that can be used to speed up drying.
To do this in a "reasonable" timeframe, my inclination would be to not seal the end grain.  Cut a bunch of rounds and let them dry for about a year until they stop losing weight.  Assume you will get cracks and splits and just deal with that.  Pick the best one to work with.
Cracks and splits aren't necessarily cause for rejection.  A common way to deal with them is to fill the gaps with resin.  Colored resin can turn it into a piece of art.  Note, though, that the resin will limit the tools you can use for the engraving, at least on the resin portion.
Carving the logo
If you have access to a CNC shop, you can give them the round and a computer file of the logo (they will typically be able to create the computer file if all you have is artwork or a bit map image).  They will be able to produce a perfect engraving, with very smooth and precise lines.
You can do this by hand; it will just require some time and being careful.  A router could be used, at least for the larger lines, but it will be hard to see what you're doing for the small details.  A rotary tool, like a Dremel, would make it easier to see what you're doing.
You could even use carving knives and gouges and do it the old-fashioned way.  Unless you are an experienced carver, those tools are likely to give the result more of a handmade appearance, which might even be better for the look it sounds like you want to achieve.  Knives and gouges won't be practical on resin, though, so if you have resin fill where you need to engrave, you could use a rotary tool in those spots.
Terminology
There are a number of related terms you could investigate.  Wood "engraving" is often reserved for fine, shallow cutting used to reproduce detailed pictures.  The lines are cut into the wood (a "negative" image).  "Woodcut" refers to a process where the background is cut away leaving the lines; it typically produces a cruder image.  Patterns of thick, deep lines are usually referred to as just "carving".


Can epoxy fluidity be changed, before it is cured? For this kind of project I have in mind using epoxy of different viscosity:

to create the "base structure" use (very) viscous epoxy - especially for the curved area; I could shape it like I could shape cement;
to create a more beautiful finish - use (very) fluid epoxy.

Of course (especially considering this answer), the epoxy should have the same chemicals, but be "adjustable" to be thinner or thicker.

Ideally, the agent should not change the chemistry (much).

I guess that the curing time is not an issue - unless it extends to days / weeks / more.

Some epoxies are more fluid at higher temperatures, at least at first.  The higher temperature also causes faster cooling.  I've used this to good effect with epoxy adhesives. A slow-setting (several hours to give a useful bond) product warmed up to about 40°C gives a very good bond as it wets the surfaces well; it then cures fairly quickly, though not as quickly as the equivalent fast product.   Conversely chilling should both thicken and slow down the reaction.  Using a fairly liquid version and chilling for the thicker step might be worth a try, however it will still slump unless restrained by a mould.

Additives are likely to be problematic for thinning: they'll be liquids that are likely to want to evaporate, so adding too much will lead to significant shrinkage; they'll also affect the cure.  Water is a bad idea - it will lead to a cloudy and weak result, but small amounts of acetone or denatured alcohol can apparently be used if you want a very thin layer.  Mixing isn't easy, which means it's likely to introduce bubbles (as it did when I tried using alcohol-soluble dies.  So this probably isn't an option for forming or casting, but may help your topcoat.

Because formulations are proprietary, you'll have to do some experimenting on a smaller scale, and hope that translates well to a large scale. Other people may have used specific
products that you can easily buy, and their results might help you get started.


Paper for Custom Book Jackets? I wanted to make a custom book jacket, but I'm not sure what paper to use. Any help would be great. I live in the UK so if you know what the paper is called over here that would be even more amazing.

I'd preferable want something with a matt finish that I can print on. I'd also like it to be relatively durable.

Another possibility I'd considered was paper than transfers onto hard cover but I have no idea where to start with that.

Thanks.

You might consider Kraft-Tex® Paper.  Many people are using it for bookbinding.  It is also used for making wallets, purses, even luggage.  It is ultra-durable (virtually rip-proof), can be sewn like fabric, and embellished in many ways including printing.  Here is the description written by the manufacturer, C&T Publishing:

Wait until you get your hands on this rugged paper that looks, feels, and wears like leather, but sews, cuts, and washes like fabric. Kraft-Tex® is supple, yet strong enough to use for projects that get tough wear. Use it to bring an exciting new texture to your craft-sewing projects, mixed-media arts, home decor, and bookmaking. Durable fiber-based texture softens and crinkles with handling and washing.
Original unwashed Kraft-Tex® is available in Black, Chocolate, Natural, Stone and White by the bolt or by the roll. (It is now available in several more colors.) So many ways to play with Kraft-Tex®: sew it, stamp it, paint it, fold it, draw or inkjet-print on it. White is a wonderful canvas for painting, rubber stamping, drawing, and stitching. Black makes metallic ink or thread, gel pens, and powdered pigments pop! Kraft-Tex® does not require interfacing.

I have purchased some and can’t wait to see what it is like to work with!


How to avoid / deal with rough edges after painting plywood? I want to make a plywood owl lamp similar to this one. After sawing the pieces and polishing them, I tried painting them using watercolours. The colour looks good, but the wood has become rough on the edges. I am afraid that polishing again will remove the colour (is this correct?). What paint would be good for this job, provided that I want it to be

Relatively transparent, to see the wood through the colour (i.e., no acrylic);
Relatively cheap (i.e. no varnish – I will use fully transparent varnish at the end, but don't have the budget to buy many different colours of varnish just for this);
Not making the edges of the wood rough.

My wood is simple 3mm plywood. For the rest I don't know any specs, but don't expect it to have any kind of quality.

When using a water based paint, you will for certain cause the grain to raise and funny things that look like tear-out on the edges.

To avoid this, before painting, I sand, then intentionally raise the grain with water, i.e. I paint it with water.

Then I sand again to remove the raised grain and the tear-out.

Finally I paint it with pigmented paint - in my case watered-down acrylic which does a nice job of letting the grain show through.


Best materials for a long-lasting scroll I'm trying to make a scroll to document life events. The important requirements are:

approximately 30cm wide by 2m tall
relatively easy for other people to sign their names on it
can be rolled up and carried in a cylindrical tube in a backpack
last at least 50 years with minimal deterioration, while being unrolled, hung on the wall, and then rolled up again at least 1-2 times a year

Wikihow has a guide for making a scroll (fabric lasts longer than paper; sew the fabric to match the size of the dowels), but no tips for making sure it lasts long.  An art store suggested I could use acrylic pens on canvas, but I also read that acrylic can crack and deteriorate from frequent rolling and unrolling.  This forum also has some tips about calligraphy on fabric, such as the idea of stabilizing the fabric with clear acrylic first.

What is the best combination of materials for this (type of fabric and type of pens)?

We actually have a good idea of which scroll materials last for hundreds of years, because we have scrolls that are hundreds of years old. What are they made of?

Parchment

We have two thousand year old scrolls written on parchment (as required for Jewish Torah scrolls). These seem to be mainly written using ordinary carbon black ink, but many (particularly Medieval) documents were written using Iron Gall black ink, of which many survive.

Parchment is expensive and relatively difficult to come by, but is still produced in small quantities.

Papyrus

The Egyptians wrote on papyrus scrolls, and we have several surviving examples including some over 3500 years old. Like the Jewish parchments, these were normally written using carbon black ink.

Papyrus is also expensive, but not as expensive as vellum and more widely available.

Paper

We have surviving fragments of paper with writing/drawing on it from the 2nd century BC, and we know that the Chinese made scrolls from this material. Chinese painting normally used water based inks for both paper and silk scrolls.

Silk

Chinese scrolls have been written on silk for thousands of years - the excavations at Mawangdui unearthed silk scrolls dating back to the 2nd century BC.

Silk fabric is readily available (if relatively expensive), but requires treatment before it can be written on.

Suggestion

Given the difficulty of acquiring and preparing the other substances, I'd suggest you look for paper. The specific type you're looking for is probably a relatively heavy acid-free paper (AKA archival paper or museum grade paper), which is specifically designed to last for a long time.

As for ink, since you only seem to wish to write and not draw/paint in colour, I suggest the ubiquitous carbon black.


How can I protect my pencil & charcoal drawings once complete? I have now built up a small portfolio of pencil/charcoal drawings. Most of the time they are kept in my folders, but sometimes they are viewed by friends and relatives. And on the odd occasion displayed at the local community hall.

I've started to notice finger marks and tiny smudges on the artwork. As none of pieces are permanently displayed I don't want to frame them.

What is the best way of preserving and protecting my pencil/charcoal art without having to put them behind glass?

One of my friends said that you could use hairspray? Is that the right way to go?

If the pieces are likely to be handled and/or displayed then using fixative sprays is probably the best option. There are two purposely manufactured types:

Workable
Final

Workable Fixative

As the name suggests, this allows you to add additional layers to your work after the spray has been used.

Workable Fixative is a thin solution and it sets up a new toothy (slightly rough) surface for more drawing. You can choose to spray the entire piece or isolated parts. To prevent other areas getting sprayed you can use paper, or frisket, to shield the areas that you don't want to spray. Once the fixative is dry you can continue working on the drawing.

The fact that it provides new tooth can be an advantage as heavily shaded/worked areas can become smooth making it harder to apply further layers of graphite/colour to the piece. So, you can use a workable fixative every few layers to keep a fresh tooth.

Final Fixative

This provides a more durable surface than a Workable Fixative, but this should only be applied once you are certain that you don't what to make any further adjustments.

However, a Final Fixative can cause the piece to darken so many artists do not apply the this layer and simply stop at a Workable Fixative.

Hairspray

Hair Spray has been mentioned as a cheaper alternative to fixative sprays. Below is a summarisation from Drawing for Dummies

  Hairspray does contain some of the materials of a Fixative but it only works for the short term, and ultimately damages the drawing - the hairspray yellows over time and ruins the drawing.

Do not use hairspray.

Applying Fixative

Use proper ventilation. Fixatives smells and is hazardous to your health.
Shake the can before spraying and test on a scrap piece of paper away from your drawing. The nozzle can clog & will deposit 'lumps' on your drawing
Directions on the generally say to spray 20-25cm (8-10 inches) from drawing. However, I spray 30-40cm (12-15 inches) from drawing. Make sure it is on a flat surface and not drafty.
Lightly spray first coat horizontally. Let dry for 15 minutes. Make sure the layer is even and smooth.
Lightly spray second coat vertically. Let dry for 15 minutes. Make sure the layer is even and smooth.
Subsequent layers may be added in alternating directions if needed.

The sprayed areas of your piece will become darker once you have sprayed it and it won't lighten once the fixative has dried.


Why are my China clay objects breaking during drying? When I use China clay for making things, it is good, but when it is dry, after some time, they end up broken. Can anyone tell me that what can I do to prevent my works from breaking during the drying process?

China clay is or kaolin is not structurally strong enough just on its own and needs to be mixed with other materials to form a more robust material that will survive the pre-firing drying period. Assuming this is happening pre-kiln. When you say " when it is dry after some time they end up broken" it sounds like you may not be firing them soon enough or not at all, which is required for them to remain solid. Otherwise they will return to the dust that they came from.


Since oil pastels require layering of colors on the top of each other, how am I supposed to see the underlying sketch? Well, for coloring narrow drawings like branches of a tree, I think we need to layer a dark color on a light color, and then scratch off the top layer from the branches area.

Problem is how would I see the underlying sketch to know where are the branches exactly!

What are my options?

If you're able, a Tracer projector could suit your needs. You place it over a small sketch and it magnifies it. No digital images required. Any other kind of normal digital projector will work too - although the resolution might not be as good. Overhead Projectors (these) are great too, either sketch onto a transparency, or you can buy special transparencies to print on. You can often pick these up very cheap, or even for free - many schools have piles of them in my experience.

Any of these methods will allow you to project your sketch over the top of your work, meaning your sketch will not be obscured.


Store paper in a humid environment As a hobby, I'm starting to do calligraphy. I've bought some paper online a few weeks ago (a Rhodia paper block). Today, I found out that when the block lays on a flat surface, I see two or three small "waves" in the paper which seem they are caused by humidity (you know when you wet a sheet of paper and where it is wet it shows some "waves", well, they are similar, but extended through the whole page and not as tall). If I detach a sheet from the block it shows the very same small waves (it's not completely flat).
I also own some other blocks, and I see the same problem (although much less noticeable) in all of them.
I live in a naturally humid environment, that's why my first suspect for this is humidity.
Is there a way to store paper in such a way that avoids this strange effect? Moreover, is there a way to make the block return flat?
Thanks in advance

You can make sure an equal pressure is applied to the individual papers or blocks while being stored by laying a heavy and flat object like a book or a similar item on top of them. Even if the humidity would otherwise warp the paper, there is no room for that now.
You can try storing your currently warped paper blocks like this for a while, but I doubt they will become completely flush again (they would need moisture so the fibres can expand, and then shrink while the pressure is applied, but the moisture would need a way to evaporate relatively quick or the paper might end up mouldy).
See also the first half of this answer for more information on storing paper.
The already wrinkled or waved paper can be straightened by moistening it and sticking it to a wooden board using water activated tape (see also the second part of this answer). After drying, you can either cut the paper out of the tape borders before using it, or write on it first, so the ink can dry completely without it warping the paper either.


How can I remove CA glues (e.g. Super Glue) from a material? I recently got some Super Glue on the sole of my shoe, while working on a craft. Luckily, my shoe wasn't on the ground long enough to be glued to the floor, but now, the entire bottle of superglue is stuck to my shoe (it's a small, 5 mL bottle).

How can I get the Super Glue (or CA glues) off my shoe (or other materials, like my hands)?

While superglue is strong enough to seal many things, it does have an enemy: acetone. Acetone is able to break down superglue bonds.

To get the superglue off of your shoe, try and use nail polish remover (that contains acetone). Be careful though, since acetone is known to be able to dry your hands quickly though. Using this should do the trick. Just remember, take your time, and wash off all the glue and nail polish remover when you are done. As acetone dries your skin, you may want some lotion handy.

As an additional aside, pointed out by CreationEdge, this won't work effectively on plastics, which it destroys, or other materials, such as wood, that may soak up the acetone.


How to regain a row of slipped stitches? Last night I was doing knit stitch on a practice piece of knitting in a small patch, 26 stitches long. When I got to the end I'd realised I'd messed up and I had 27 stitches. The yarn I'm using is very old (my mother in law gave me it to practice with but she last used it to make my husbands baby clothes...!) and a little frayed but not too bad to use, but I couldn't see where I had gone wrong even with most of the stitches being rather clear.

So in my infinite wisdom I un-did the last row thinking I could slip the needle back on and then go again, but this ended up with me being completely unable to get the needle back through the stitches. I tend to knit too tightly at the moment (I'm a beginner and only been doing this about 3 weeks! I tied off on the end and kept the knitting for reference but have since started a new practice patch).

If I slip a row off a needle like that, by accident or on purpose, how would I get it back on?

When you have a row of slipped stitches that are too tight to fit back onto the original needle, you can pick them up on a different needle, such as:

Use a much smaller knitting needle. Eg, if you knitted originally on US size 8 needles (5.0 mm), use a US size 4 (3.5 mm) or smaller needle to pick the stitches up. The smaller needle should fit easily through the tight stitches.

If you don't have other sizes of needles, look around your home and see if you have something that could substitute. It just needs to be stiff and skinny. Like a bamboo skewer for cooking.

Use a 16" circular knitting needle. If the stitches are not too tight you can use the same needle size as the original; otherwise use a smaller needle size. Circular knitting needles have a short portion that's the regular thickness of a knitting needle, then a portion of narrow cable. Once the stitches slide over the regular needle onto the cable, you get a little bit of slack because the cable is so much narrower than the needle. (The reason to use a 16" circular needle is that 16" circulars have a shorter portion of regular needle thickness than longer circulars.)
If you don't own a smaller size of needle, use an embroidery needle and scrap yarn. Tie something on the end of the scrap yarn to stop stitches from sliding off. (Lots of things can work for this: a large bead, a pencil, a wristwatch...)
Pass the embroidery needle through each stitch just as if it was a knitting needle. Once all the stitches are safely on the scrap yarn, you can safely transfer them to the original knitting needle. Or if they are extremely tight, transfer them to a knitting needle a size smaller than the original.

Now that the stitches are all on a knitting needle, them with the original size of needle.

PS: On your next project, work on not knitting so tightly. It takes some practice but it will pay off in the end.


How do I make pom poms not fall apart as easily? As we learned in How to make a pom-pom? they are fairly easy to make. The problem is that they are just as easy to take apart.

So you could get your pom pom trimmed to make the perfect sphere and it takes little to no effort to pull individual strings from the ball. Do this enough and the integrity of the ball starts to fail and exacerbates the issue and they can start to fall out on there own.

I noticed that all of the commercial products that use pom poms e.g. clothing, toys, etc. do nothing to prevent this (Wife hates it when I test them). That tells me it is not a huge issue that industry, as a whole, does not attempt to mitigate it. It's not that can't. I'm sure its a matter of cost justification and its not worth it.

However, when I make something I would like it to last as long as possible.

What can I do to reduce the likelihood of a pom pom falling apart? Or at least slow it down. Glue comes to mind.....

If you want to make the pom-pom not fall apart as easily you have to pull the string tighter when making a knot. Some tips to consider:

loop the string about 3 times before making the final knot
use your finger to hold the string in place when making the knot
try using a different (not yarn) string for the knot – a thin and strong one (so that it doesn’t break when pulled tight)
if you are using the same yarn to tie the knot as the one the pom-pom is made of, and you are using natural yarn, then try soaking the knotting string (just that string) in warm/hot water and make the knot while it is still wet (it should shrink when it dries, giving you a tighter knot)

I guess the reason why pom-pom manufacturers don’t do anything about it being  easy to pull separate strings from a pom-pom is because pom-poms are not meant to have their strings pulled out one by one, and they turn out to be just fine if you don’t do that.

If you feel like you need to use glue anyway, try it, and share your results.


Why isn’t a orthographically projected plane at 45 degrees seemingly half its actual length? We have a plane of certain dimensions X and Y, and are looking at it perpendicularly by means of orthographic projection. The plane rotates 45 degrees on the X or Y axis.

Given this situation, I would expect that the plane, once it has rotated, would appear to have half its original dimension opposite the direction of rotation (rotation on X-axis would change the apparent length of Y); or that the plane shrunk by 50%.

In short, I would expect a linear transition. Why isn't this the case?

For example, a vertical plane (geometrical entity) seen from the front of an orthographic system will shrink on the horizontal axis due to rotation around the vertical axis until it becomes invisible, but at middle point of rotation, the projection will be longer then half of the actual length.

How come is the projection shrinking in the first place?

Top angle rotation implies movement in 2 axis, in this case upwards and to the left. However, because from the front angle the up vector becomes backwards vector, the movement on that axis will not be visible in projection. That leaves only movement to the left to be projected, therefore the plane will shrink horizontally.

At what rate is the shrinking?

The change in size happens gradually (not linearly), first slower, then faster, or vice-versa, because the trajectory is an arc, not a straight line.

2.1. How to geometrically describe an arc/circle?

An arc can be simplified by using equal segments. Every segment has a certain angle, depending on it’s length, and the next segment inherits the angle and is rotated still by the same degree.

2.2. Why does the trajectory matters?

The closer the plane is to 90 degrees (to the projection plane) the smaller the projection, and the closer it is to being parallel, the closer to actual length. If every projected segment has a different, increasing angle, the length will grow bigger with every increment of the arc. This is the projection of the rate of shrinking..

If the trajectory would be a straight line at 45 degrees, then at 45 degrees the projection would be at half the actual length. However, this means the plane would have to shrink.

In conclusion I would like to add that this is a matter of rotation and it is valid in perspective as well. However, in perspective translation also marks the scaling of an object. I think foreshortening refers only to translation, not to rotation. Nevertheless, a projection can change size according to rotation as well.


Varnish with flash point over 40 °C — safe on painted mugs when heated? I've painted regular white mugs and want to varnish them too. But my varnish has the following specs:

Gloss varnish based on alkyd resin.

Flash point: Above 40 degrees Celsius.

Is it safe to varnish on some sections of the painting on the outside of a mug? Or will it catch fire if microwaved to boil water or something?

I have no background in chemistry.

Honestly, you should be using glaze and not varnish.

I get that you're just trying to protect a painting outside the mug, but even if you just wash it by hand, a varnish is likely going to break down much, much faster (especially with heating it) than a food safe glaze which can be applied to the whole mug creating a seal to protect everything and can often be washed in the dishwasher and heated even in an oven if you so desire and it won't damage it.

The caveat is that it probably would need to be kiln fired, but considering the prevalence of paint-and-take ceramic shops nowadays, you can probably find one that'll let you pay a fee to glaze and fire it for you so you don't even have to buy the glaze for one project.


How to make chewable silicone beads? I've been searching for an answer for this, and can't seem to find it!
I've read a couple other posts about casting silicone, but no answer quite fits what I'm looking to do.

I have an autistic child who "chews" on everything. I've looked into buying the "chewlry" that is made for children to chew on (chewable jewelry) similar to a baby teething ring, but I want to figure out how to make this jewelry myself. The chewable jewelry is made with silicone beads. However, I cannot find directions on how to make the silicone beads anywhere. All of my searches result in "how to make silicone molds for beads" I do not want to make the mold, I want to make the bead from silicone.

Also, I saw it previously mentioned that adding a binding agent to the silicone to increase durability would be a good idea. What type of binding agent should be added to make the beads durable and safe for a child to chew on?

I've used a food grade silicone in the past that has the consistency of pudding. It is rather soft and very weak and would not hold up in the example you provide. I have used a more expensive silicone, also food grade that requires substantial mixing to get good results, often requiring vacuum degassing for smooth surfaces. In your example, I expect that small surface bubbles may not be a problem.

In order to ensure my information is correct, I did a quick search for food grade silicone and discovered that Smooth-On is still in business and provides various degrees of Shore Hardness levels.

The second link shows that Smooth-On 960 has a Shore of 60A, which equates to the hardness of a typical automobile tire. That's pretty hard, but that's also an opinion.

I have a silicone mold in hand, which can be gripped and torn, but I don't recall the hardness figures, making it only slightly useful as an example. A spherical part produced from a mold will be more difficult to tear as it is going to have fewer gripping points (none) unless otherwise damaged.

A search for binding agents results in products used to release parts from molds, not useful in this case.

Regarding your mold making question... silicone sticks only to itself. You could make the mold from anything other than silicone and pull the beads after it cures. I have a lead shot split mold that is a series of cavities with tiny funnels into which molten lead is poured. That mold could be split open (empty), immersed in the silicone and then closed and set to cure. It's not a recommendation, as I would not consider the mold to be food safe.

If you have a makerspace in the area, or use Craigslist, you may be able to find someone willing to 3D print a mold from food-safe filament. The mold could be akin to the lead shot split mold but far safer for use in the manner desired.


Is this the 'Weaver's Knot'? I'm trying to remember a knot that I learnt in a crafts workshop to build a himmeli : a himmeli is a construction in straw (example image), a thread goes through the straw to keep it together. The knot I learnt was to join a new piece of thread, when you ran out of thread.
The knot I was taught was called "Kankurin Solmu" in Finnish (it translates to "Weaver's Knot"). I found the following diagram of the "Weaver's Knot" on this Finnish web page, but I just can't make out how it is built from the diagram.
Do you think that the knot in the photo I posted below corresponds to the so-called Weaver's Knot of the diagram at that page? (Something doesn't seem quite right to me but I can't exactly remember the knot I was taught and I can't really make out the diagram).
Does the knot in the photo of my post seem viable as a knot to join thread?

Click image for larger version

The knot on the web page you posted looks like a basic square knot (aka reef knot) to me, at least as far as the end result is concerned. (They're tying it upside-down for some reason, but they're ending up with two simple overhand knots, one right, one left, and that's gonna get you a square knot.) One of the square knot's main uses is to join two pieces of thread/yarn/string/rope, so it can certainly be used to tie in a new piece of thread while weaving.
What you're tying looks like maybe a strange configuration of a granny knot, which is not likely to stay put if you pull on the ends.
An actual "weaver's knot" does exist, but doesn't look like either your image or the website you linked to. It's also called a sheet bend, if that helps.


Is there a purist method to join/lock the edges of an origami magic ball so it's still squishable? So, I've completed my first origami magic ball, but the youtube videos I was following end with using blue painter's tape on the inside to join the edges of the waterbomb tessellation together. While it works, it's visible, and not particularly clean or a "purist" (no cuts, no glue) way of forming the ball.

I've read that you can overlap the first and last columns of waterbombs and glue the edges together to get a cleaner look. But is there an origami-purist method (i.e., folding only, no glue, no cuts) to do this that will lock securely enough so that you can still squish the ball without making it fall open? Or is a glue/tape the only option if you want this to be an action origami?

For certain corrugations which are "rolled" in order to get an object with rotational symmetry, you can overlap the two edges of the paper and have the model keep its shape. However, I doubt this would work with the magic ball since it's an action model. Its point is to be squishable and just arranging the layers one over the other prevents this in two ways:

Squishing introduces a lot of tension which just arranging two corrugated edges above each other can not withstand.
Overlapping multiple layers introduces some asymmetry: if you overlap just a single row of the corrugation, you create a stripe which has two layers of paper while other places have just one. This will cause any deformation to not be laid out equally over the whole model, and this will not only look bad but also locally increase the tension which makes the model come apart. Using more rows than just one in order to make a stronger lock only increases this effect. Perhaps if you use a sheet twice as wide as the original in order to get exactly two layers of paper over the whole surface, it might be enough to withstand some squishing, but the layers would come apart along the free edge anyway.

Basically, if there is a long free edge, this technique might work for static models, but not for a squishy ball. So, the only way forward would be to get rid of the long free edge. Imagine we were not folding a corrugation but just forming a cylinder out of the sheet and wanted it to stay in one piece. You might try to make pleats around the perimeter of the cylinder so that there are many short spans of free edge instead of one long span. The wall of your cylinder would then look something like this:

    |
  ^ |
  |||
  |V
^ |
|||
|V
|

Joining two edges when the walls have such pleats would probably work. Now imagine treating this pleated paper as if it were a plain sheet and folding the corrugation on that.

I haven't tried this in practice but it might work.I am, however, afraid, that in practice these extra layers would change the behavior of the structure, and in practice you would still get noticeable artifacts.


How to open a hot furnace without damaging it? I have a heat treatment furnace which is very similar to furnaces used to make jewelry, such as to melt gold, silver and other precious metal alloys for casting into jewelry. In fact, the manufacturer's operational video actually shows the operator putting a crucible into the furnace, which has a front loading door. This type of furnace is sometimes called a "muffle furnace". It looks like this:

So, my problem is that the operating manual says not to open the furnace if the internal temperature is greater than 300C. However, if I wait for it to cool down, then my material will begin to solidify.
Now, I haven't really tested it, so maybe the chamber can be made to cool down rapidly so I can withdraw the material when it is still hot, I don't know. But I am asking here to see if anyone else has run into this problem and have a solution? According to the manual the risk to the furnace of opening it when it is hot is thermal shock which could cause the lining to crack, but that seems kind of unlikely. The lining is pressed ceramic fiber which as I understand it is pretty stable, but I don't want to second guess the manufacturer, though.

There are ovens made to be opened when hot and there are ovens not made to be opened when hot.
From what you mention what the manual says, yours can not be opened when hot.
As there are different parts that go wrong at strong heat loss or getting the full blast of the oven heat, it is impossible to predict what your oven can handle and whether you can adjust it.
Your best bet is to replace this oven with one made to be opened when hot. Your second best bet is to ask the maker or a community of oven users where someone may have more knowledge.


Repairing a detached cover on an old leather-bound, sewn book with marbled end papers I have a beautiful old book from 1869 which, greatly to my chagrin, has been damaged: one of the boards has come off. I would like to repair the book, or at least understand enough about how it ought to be repaired that I can shop around intelligently for someone to repair it. Is is possible to re-attach the board while preserving both the beautiful marbled end papers, the solid old-style sewn binding, and the elegant leather cover? How would one approach such a repair? (I am somewhat conversant in book repair and binding terminology, but not skilled in it.)

Definitely don't attempt to repair it yourself - I can't tell for sure from the photo, but I think this is a hollow back binding. In this style of binding the covers and the spine were build directly on the book block, not glued together separately and "hung" into the covers as is done with modern hardcovers. That makes fixing a (partially) detached cover harder.

In a modern hardcover, you would fix this approximately by:

detaching the end paper from the book block on the broken side,
lifting about an inch of the end paper from the coverboard,
pasting a strip of cloth or thicker japanese paper over the torn cover joint,
pasting a strip of thinner japanese paper over the torn end paper joint ,
reattaching the end paper to the cover board and the book block,
and optionally, painting the new material paper to match the surrounding if it's showing through.

Better hardbound books will have the book block attached to the covers not only by the end papers but also by paper,cloth, the ends of the tape/ropes the book block was bound on, etc. These can stay attached, since you can paste the patch over/around them.

In a hollow back... I'm not sure, to be honest. I never actually made one, although I know the approximate steps, and I definitely never tried to repair one.

The main catch is that since the spine is constructed directly on the block, you can't just detach the end paper to get access to the joint. My best guess is that you would still detach the end paper from the book block; then you might need to cut a slit between the book block and the spine hollow to insert the patch. In best case scenario you would want to avoid opening the hollow, but rather insert the patch between the layers of the back "board" (it's not actually a board, it's several layers of paper pasted together).

If you plan to get this book repaired, definitely check the credentials of the professional. Check their portfolio if they have it, ask directly if they ever worked with this type of book. Hollow back binding is very common on older books, so you should find someone easily, but I assume it would be also easy to be a "professional bookbinder with book repair experience" without ever getting your hands on one. If you don't want to alienate the person, be the curious book owner and ask what kind of binding this is - the right kind of bookbinder will tell you a lot more than I could ;)

Also, if this is the only damage the book has and you don't use the book often... maybe the safest thing would be to leave it be. It doesn't look like a big tear. Store it in dark, dry place, avoid non-archival materials and pests, and it will be alright for a few more decades.


How can one blow/work with borosilicate glass to a container of precise dimensions? I am a poor graduate student who is wishing to make a container out of borosilicate. I need pretty tight control over the final shape. Is it possible to work a piece of glass to a specific spec by hand?

I want to make a perfect hollow cylinder that will serve as a tank wall, for starters. I have access to a craft center through my school and willingness to learn. I was going to sign up for a class but if this is a pipe dream I will find another means.

UPDATE

I found a website that has some of the techniques I wish to employ see the following link. I am still wondering how well one can control some of the dimensions. I would be shooting for pretty uniform cross sections. Also they all start with the glass in a tube-like geometry already. How do you even make that from scratch?

Borosilicate also goes by the brand name Pyrex. If you perform a search for "borosilicate glass cylinder" you will find some sources of various sizes of tubing.

If you have access to a sufficient powerful heat source, you can heat the tubing and force it to close.

A quick bit of research shows the working temperature to be 1245°C, attainable by MAPP gas torches at the consumer level. If you know someone who does gas welding, oxy-acetylene torches will reach the necessary temperatures at a lower cost overall.


Can I use cartridge ink for dip fountain pens? I understand that ink in fountain pen cartridges is a bit thinner. Can I still use it for dip pens if I squeeze it out of the cartridges? I have an excessive amount of this ink, and might not go back to using cartridge fountain pens.

If it doesn't work right out of the cartridge, can I mix something in it to make it usable? Or evaporate it somehow?

Due to the many different kind of quill pens nib designs, I don't think any definitive yes-no answer is possible here.

Generally, yes, ink will flow.

What kind of writing you want to do will have much influence on the decision about whether you use it.  Probably the best choice is to experiment by having a few controlled dips, and creating a few controlled strokes.

Dip to a fixed-depth, and the draw the pen nib down a page until it is exhausted.  Make multiple strokes as needed.  Repeat this for varied dip depths.
Then try letter-writing.
And / or, try other common nib-strokes related to the kind of purpose you will employ the pen.

If you find a writing style comfortable enough — problem solved.


My double knitting pattern is confusing me A pattern I’m doing has double knitting in it.
First off, how do I unravel the cast on stitches w/o unraveling the first rows?
Second off, it says that all of the stitches go onto one needle, but then it has the pattern. Do I need to switch the back colors to the back needles? How do I do that?

If your pattern tells you to unravel your caston, it should have also told you to start with a provisional caston. A provisional caston is a method that allows you do easily unravel the caston, turning the beginning of the work into live stitches. Here's a link to one method of provisional caston.
It sounds like maybe you didn't do a provisional caston (oops). If that's the case (regardless of whether it's your mistake or the pattern designer's), you have three options to fix it.
Option one: Pick up and knit stitches from the caston edge, just like you would pick up and knit stitches along any other finished edge. Here's a source with a photo tutorial. This is by far the easier method, but it will create a ridge or seam that will be visible on the wrong side of the work. The ridge might be completely invisible from the right side of the work, or it might not. It might also be less stretchy than the rest of the work. I recommend you try this method first, and see how it looks and stretches. If you're not willing to tolerate the ridge, rip out your picked up stitches and use the next method.
Option two: Start by threading a knitting needle through the first row of stitches. It might help to use a smaller size of needle than the one you cast on with. Now find the end of the yarn and start undoing the caston edge. This means finding the next bit of yarn above the loose end, then pulling that bit of yarn until the loose end comes through whichever other bit of yarn it's looped through. Repeat. It will be a slow, painstaking process, and you will quickly learn why special provisional caston methods exist.
Note: it's probably not worth the effort to unpick the caston edge. You will very likely get several stitches in before you want to say "F--k it!" and give up. At that point, you can just leave the rest of the caston edge as is, and use the stitches that you picked up already. Some of your stitches here will have a ridge on the wrong side, and some of them will not.
Option three: Insert the knitting needle through the second row of stitches. Cut the yarn through a stitch in the first row, and unravel that first row. (I know you said you don't want to do this, but it may be your best option at this point. Try the other methods, and come back to this one if they others don't work for you.)

Yes, double knitting is worked with both sets of stitches on one needle. You can set it up by putting all the stitches on one needle, alternating one stitch from the front needle, then one stitch from the back needle, etc. Or you can start with the stitches on two needles, and work the first row, alternating one stitch from the front needle, then one stitch from the back needle. At the end of this row, all the stitches will be on one needle.


Making thin brittle sand design that holds together I'm trying to make pretend coins out of sand, so that they are solid enough say, to hold it by the edge and it not bend, but brittle with so that if I crushed it in my hand it'd crumble back into sand.

At the minute I'm trying to do this by mixing various consistencies of pva glue and sand, and am getting close but it's just not as brittle or as solid as I'd like it.

Ideally I'd like it to be in similar consistency to say that of a cracker or ryvita - which I would use for this project except that after it is crushed it should appear as close to sand as possible.

Any advice would be greatly appreciated, thanks :)

Some extra details:

I'm using sand bought for arts and crafts that I bought on eBay, so the sand is very fine. As for ratios / consistencies, I've tried with PVA glue and rubber cement (seperately) with 2:1, 1:1 and 1:2 ratios with the sand (roughly). Too little PVA and the sand doesn't stick, too much and it becomes a bit 'floppy'. I didn't know if there was a different type of glue I should try, or with a mixture of something else. I've also tried with kinetic sand, but that doesn't break as well as normal sand.

My most recent attempt I used a lot of PVA glue to sand, which worked but was slightly floppy - however I then coated it in metallic spray paint which seems to have made it hold together solidly. I haven't tried crushing it yet to see if thats even possible, but could the spray paint on its own potentially be a solution?

Fascinating project. The solution was right in your question; make it like a cracker — flour.

You're essentially making a sturdy paste instead of a glue. I mixed:

3 parts sand
1 part all-purpose or bread flour
Water, just enough to wet the sand

I drained off any excess water, packed it into a mold and let it dry in the sun (1-2 hours?). I guessed at the proportions empirically, but it worked great!

The disc to the right is a failed experiment with cornstarch

The coin was pretty solid… yet breakable. I could carry it around and drop it from a few feet without breaking it, yet I could snap the disc with a bit of deliberate force, and crush it down into sand by pounding it or working it between my fingers.

  …after it is crushed it should appear as close to sand as possible.

Bonus that you're not adding anything permanent or inorganic to the sand. I could not see any flour when I crushed the coins back into sand, and dropping it into a cup of water broke it down completely (which makes it easy to pour off the flour-silt, if that's important to you).


Pack kusudama flowers bouquet for shipping What is the best way to pack paper flowers for shipping?

I was thinking to use packing peanuts and some newspaper but I'm not sure if this will work and my bouquet will arrive without bents or big damage.

Thank you in advance!

You can use wire to make the bouquet stay in the middle of the shipping box without touching the sides by attaching the firm part of the bouquet to the sides of the box with it, then adding newspaper, etc. (again to the base), to make sure it doesn't move, just in case.


Can a pizza cutter cut through fabric? As can be seen in this video, a CNC machine uses a cutting wheel in order to cut through fabric. That tool resembles a pizza cutter.
So can a pizza cutter cut through fabric? If so, what kind of fabrics is it able to cut?

Unlikely.
There's a reason people keep separate fabric scissors from their regular scissors--cutting through fabric requires a very sharp blade, which you're unlikely to find on the average pizza cutter (designed to cut through soft cooked materials).
What you're seeing is a rotary cutter, a circular blade on a handle that's sharp enough to cut through fabric. Unlike a typical pizza cutter, rotary cutters come with blade guards and retractable blades to protect the user from cutting themselves. They're frequently used by quilters, who need to cut many pieces with straight lines, often using heavy plastic templates. In the images shown on the blog Quilter's Review's review of several cutters, you can see the safety features on the handheld rotary cutters. The CNC machine is using a similar blade, but as it's not being handled by a human directly, the need for the additional safety features is reduced.


What is the equivalent to niello for brass? I have some brassware with nice engraved designs that I'd like to bring out. If it were silver or gold, I'd use niello, but that apparently doesn't work on brass. I could try and do something to oxidise the whole surface and polish the oxidation off of the high points of the engraving, but ideally I'd like something darker.

I can see from pieces like this:

Engraved lamp stand from the Met Museum, public domain

that such a finish is achievable, but the entry just lists it as

  Brass; cast, engraved, and inlaid with black compound

So, what is the equivalent to niello which can be used to selectively darken recessed areas of a brass object?

I'd prefer more traditional methods, as opposed to simply spray painting the whole thing black and rubbing it off the high points, if possible.

I think you will have to age the alloy first, and clean the higher areas afterwards.

For tarnishing, you can use Palmolive, or any kind of washing liquid that has sulphates in it.
Another, more aggressive option, but only viable for solid, thick brass objects, is to use ammonia.
The most traditional choice, however, would be to use a mixture of salt and vinegar.
In all cases, you can leave the brass object in the liquid for an extended period of time, or rub it in with a piece of cloth, which will give you more control.
After the tarnishing, you can use either ketchup, a mixture of vinegar, salt and flour, lemon juice, or soap, to brighten the brass again.


Are "oil colours" the same as "oil paints," or am I buying pigments by accident? I was looking at these oil colours from Winsor & Newton and was just hoping someone more experienced could confirm that "Oil colours" = "Oil paints," and that I'm not inadvertently buying pigments that I need to mix with something to get the actual paint.

Basically, adding oil to ground pigment will turn it into oil paint; adding acrylic to ground pigment will turn it into acrylic paint; adding water to pigment will turn it into water colours...

So, this should be oil paint if it contains oil, and not just pigment.

(Where did you find this? Isn't there a description to the product? An image? If this is what you've been looking at, yes this is oil paint.)


Extended Fortune Teller With > 4 Flaps How would I go about folding a fortune teller with more than 4 flaps? I already know that it is possible to cut-n-tape two fortune tellers together to get this:

But, how would I go about folding something like this without using tape?
Also, supercalifragilisticexpialidocious hats off to you if you show how to fold fortune tellers of different sizes. A random example of this could be: if you could explain how to fold fortune tellers with a side number that is a multiple of 4 then that would be amazing.

How to fold a fortune teller:
Fold all four corners to the center and turn over.
Fold all four corners to the center again and turn over. To make a modular unit fold all four corners to the center once more.

On opposite sides draw a capital A on the pockets

Join the A pockets

Fold each connected pocket in on itself to hide the A and lock the model together

Fold each module in half as you go

Connect the last pocket the same way

Fold three fortune tellers for the five sided one and eight for the eight sided one.
Incidentally this makes a quite beautiful flexible model as well as a functional fortune teller

Happy folding, Grace.


What are good tools for carving in cork? What are good tools to carve in corks?

Actually, I'm using a simple kitchen knife but I guess there are better choices.

My goal is to carve some chess pieces.

I would lean toward scalples/X-Acto knives.  They a are very sharp, and the blades lend themselves to carving small details well.  They are designed for detailed work unlike kitchen knives which are designed to cut things up.

As Camil pointed out in the comments, a heftier blade might be needed to start with the larger roughing cuts so it doesn't snap.


How do I replicate this misty spray paint texture/pattern? I am restoring some old Microscopes and the existing coatings are in poor shape. I would like to strip the castings and refinish them to look as original as possible. Unfortunately, I am unable to determine what coating or process was used to achieve the fine water mist texture as shown:

Is there a paint or process available to achieve something at least close to it?

If the material is metal, one can use a wrinkle finish powdercoat to accomplish this result. It's not quite exactly the same texture, but wrinkle finish powdercoat may qualify in that it's random and irregular.

Using search terms "texture powder coat" provides a number of similar finishes, including hammertone and silver vein, the latter shown below:

If there is a powder coating service in your area, they can advise of the available finishes. You can also purchase a home powder coating system which can be used with an inexpensive (yard sale) toaster oven for small parts.


How can I make my own perforated edge? I'd like to make my own perforated edges on paper, so I can tear certain designs instead. I don't like the odds of tears when I just fold back and forth, and I don't want to use cutting in this case.

I'm making some small books and I want to take my printed pages and make them easy to tear out. But some pages might have tear-out shapes, as well.

Is there a tool I can use to easily make perforations instead?

A sewing machine without thread does a great job at making a perforation in most paper. Depending on the settings it can be rather coarse, or quite fine. Much of this will depend on what stitch types your machine is capable of. I would not use your nicest needle however, as it will most likely wear prematurely.

Otherwise, there are purpose built perforators available for ordering online, that work much like a rotary paper cutter, with the obvious difference that they do not completely sever the paper.


Wooden panels start to shift I made a table and screwed the panels together via two separate wooden bars and even with one aluminium bar. I did that in the base room. Now the table is in my flat and the panels are moving away from each other though I used large and thick bolts..  why is that?

The table from bottom:

Table from top

The short answer is the wood is shrinking as it loses moisture. Because you've used two fastening points across the width of a top board, one or more of those top boards may split as it continues to shrink.

Accommodating this sort of change in dimension (which continues to happen seasonally, even when the wood has fully "dried") is one of the classic challenges in constructing furniture from solid wood.

There is a lot of literature out there on this topic. Here's the first link returned from Google on "furniture accommodate wood shrinkage"
https://www.extension.purdue.edu/extmedia/fnr/fnr-163.pdf

Note that it's both shrinkage and expansion that cause problems.


What materials can I source to make a shiny/rubbery blue raincoat? I am interested in sewing a raincoat that looks a bit old fashioned- rubbery, shiny blue. The closest thing I could find was the image I've included. My problem is that I have no idea where to get fabric like this. I've looked locally and online, and I haven't really found exactly what I'm looking for. Any advice?

It's strongly likely that you are seeing what I know to be oilcloth. Per the link, it is close-woven cotton duck or linen cloth with a coating of boiled linseed oil to make it waterproof.

Using oilcloth as the search term, I found a few locations online for purchase. As your post referenced the blue color, I focused on that specification:

Oilclothbytheyard.com

It's likely you'll find other resources as well.


How to paint a ghost with oils? I'm a beginner, and I'd like to paint a ghost with oil paints. The effect that I want is something similar to this picture:

The only difference would be that my ghost should be purplish. But that's only a detail, I suppose.
I'd like to know the steps I should take. For instance, for all I know, I would start by painting the landscape — all of it — which in this case is a forest. Then, once the paint is dry, I would add my ghost with a very thinned colour.
Questions:

Is this the right procedure?

What thinner would you recommend? Can I just add as much thinner as to get an almost transparent colour?

I also read that thinned paints should not be used as last layer since they tend to crack. So, how can I avoid this?

Painting the background first and then adding the ghost indeed sounds like the right procedure. That way you'll ensure the transparency of the ghost is realistic.
Like you mention, be sure to let the background dry long enough first before proceeding with painting the ghost.
To thin down the paint, I'd recommend simply using a little additional oil and even less solvent, or glazing the paint.
Even though increasing the amount of oil will increase the drying period - and you need to store the painting horizontally in a dust-free environment during this time - the risk of ruining the background is minimized. You can add quick-drying medium to speed up the drying process.
Using excessive amounts of oil in relation to pigment and solvent might cause the dried paint to be glossy, so to prevent this you need at least a little thinner in the mix.
It's hard to give straightforward advice on the amounts, though, since there are a lot of variables weighing in here. You can always experiment with processes like these by replicating them using similar materials.
If you use a thinner, paints already applied (in the background) might dissolve, depending on the drying time and pigments used, and mix with the current layer (the ghost), potentially causing both layers to lose their integrity.
As for the type of thinner, it doesn't matter that much when mixed with larger amounts of oil, I think. I've used turpentine and white spirit, and am currently trying out lavender (or spike) oil, which acts as a solvent, but is environment-friendly and non-toxic. It dries somewhat glossier than the other solvents when using it for glazing, in my experience, however. For that matter, if you have a well-ventilated workroom, I suggest white spirit, as it is the most matte-drying, and I think it dries the quickest as well.
Of course, if you plan on ultimately varnishing the painting using a glossy varnish, all these comments on the specularity of the paint mixtures don't really matter.

I also read that thinned paints should not be used as last layer since they tend to crack. So, how can I avoid this?

That's very strange advice, and the context seems quite important to me (e.g. what defines "thinned"?). Can you find that passage again?
As far as I know like almost all other painters, I usually thin all of my paints. The application of oil paints is based on this premise; since oil paints generally are no longer mixed manually by artisans, the manufacture of tubed versions necessitates they be highly concentrated, to facilitate their use (we can't practically increase the concentration, but we can thin it down).
The fat-over-lean rule applies here, meaning the closer you get to the surface layer, the fattier the paint applied should be to prevent it from drying before the underlying layers have dried. This can mean that the oil paints are used increasingly pure from the tube (as opposed to being mixed with thinner, which will make them leaner), but the artist can also decide to add additional oil.