16

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?

  • 1
    Very interesting question. Do you have any specific examples of ratios or consistencies you have tried. Have your issues been you have been making it too hard or too soft? How are you making your mixture and what sand are you using? Just whatever you find outside? Curious about the micron size is all. – Matt Nov 17 '16 at 1:01
  • 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. – Dan Nov 17 '16 at 1:22
  • Thanks for the extra information Dan. I would edit that into your question as it is good information that shows what you were trying exactly. – Matt Nov 17 '16 at 4:23
  • How long to you expect a "coin" to hold together before you crush it? – Matt Nov 17 '16 at 4:28
  • @Matt I've updated the question as you suggested - as for how long I'd expect it to hold for, it doesn't need to stay together long, I imagine it'll only be briefly handled before being crushed. However I would want to make them in 'advance' as it were, so it'd need to stay together until its time to use it. – Dan Nov 17 '16 at 11:48
13

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).

| improve this answer | |
  • This sounds awesome; I'm going to give it a go now. How much water did you use? I'll have a little play around with it, thanks! Do you think the coin could be sprayed / painted and maintain consistency? – Dan Nov 17 '16 at 19:12
  • @Dan I drained off as much water as I could, so essentially just enough to wet the sand. Then I added the flour. And, yes, I there are a variety of spray varnishes/paints that would make the sand creation reasonably permanent; anything that wouldn't "wet" the sand too much. There are folks who do this with sand sculptures. – Robert Cartaino Nov 17 '16 at 19:14
  • Ahhh thats where I potentially just went wrong then :P Okay cool I'll begin again. As for making it permanent - I still want it to crumble like sand, but just be as "coin-like" as possible, so I have some metallic silver spray paint which comes out quite nice. – Dan Nov 17 '16 at 19:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.