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Picture of Wacom Pen Holder Hand AKA Making a Plaster Cast of Your Hand
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This project started off having nothing at all to do with a Wacom tablet, rather a solution to the problem of a couple of old mannequins with not enough hands between them.

It may have been easier to source a hand from another mannequin but a) a lazy online search yielded nothing helpful, b) this is Australia and useful things can be hard to find and c) why make things simple when it can be over complicated!

And so I decided to create a new left hand for the male mannequin using my own as a model. I'm female, but my hands are big enough to pass for a man's.

Researching the creation of plaster cast hands led me to using alginate as the casting material as it's skin (and mouth!) friendly, flexible enough to allow your hand to be removed once set and can be broken off afterwards, liberating the plaster object. Plus it's minty.

The plaster choice was merely due to there being a harder option than normal plaster at the shop and I thought why not. Normal plaster should work fine though, provided it's mixed right and you're gentle with it.

Step 1: Container to Hold the Alginate

Picture of Container to Hold the Alginate
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I hit the hardware store and the best option for something disposable, narrow and deep was 2 plastic pot plants hot glued together by their rims and the drain holes glued closed on one. I cut the bottom off the other pot to make an open end.

Any container the right size will do the trick really, and you may not have to cut it off to release the mould if it's the right shape.

bpark100014 days ago
Dry the plaster COMPLETELY before attempting to paint. You can put it in an over set at 120F for several hours. The plaster will get stronger and the paint won't peel off in time.
When releasing the hand from the alginate, use a straightened paper clip to poke holes from the bottom into the tip of each finger. This will allow air entry.
huplescat (author)  bpark100010 days ago
This is a great tip, thanks! Is there a point at which plaster will crack in the heat? Will any air bubbles cause a problem?
Yes, if you heat it too hot, you will essentially reverse the plaster's setting and turn it back into a powder (this is referred to as "calcine"), but this won't happen at 120F. Air bubbles won't be a problem at this low temperature. The secret is to have it heated to 120F and with circulating air so the water vapor can escape. Plaster's strength more then doubles when it is properly dried. In addition, trapped water inside the plaster will lift off paint as it attempts to escape from inside. See this link to US Gypsum recommended drying scheme. (You don't need to get this fancy, but keep the process in mind, and allowing a lot of time for drying will make up for lack of fanciness).

http://www.douglasandsturgess.com/HowTo/Drying-plaster-Howto.pdf
Zaacharia13 days ago
Hah! In stead of making the hand out of plaster, I can make it out of wax then, using the lost wax method, cast it in glass.
Also, many years ago I used alginate to make a life mask; the first one came out full size; then the mold shrunk and I made a mini-me life mask. Since my kiln is only 8x8x8 I can't cast my life mask in glass.

All you mold makers, if you can make a mold of it, you can cast it in glass - provided you have the heat.
huplescat (author)  Zaacharia10 days ago
Nice! That'd be a lot of fun :)
I enjoyed this instructable. Years ago I had a female torso mannequin I kept in the front seat of my van - I did buy her a nice blonde wig. Talk about photo ops! - having a camera catch the expressions of passers by . . . Hmm replace one of her eyes with a camera . . .or a small camera on he right ear.
huplescat (author)  charlessenf-gm10 days ago
I have been wanting to do this, but hesitate knowing that the kids would probably refuse to get in the car if there was a mannequin on board and I was giggling maniacally over it.
I assume the alginate is fairly waterproof once set?

To estimate the amount if plaster needed:

Fill your mould with water to the level you want the plaster.
Pour the water into a marked container of some sort (measuring cup, pitcher etc).

Heck, maybe just use the water that came out to mix your plaster.
I would assume it's waterproof given it's made for dental applications it'd have to be :) Some of the colour from the alginate did transfer to the plaster, but I think that was just the dye itself.

It would have made sense to measure the amount needed a little more exactly, but I often just go with the flow and wing it. It *usually* works out fine...
tomascco14 days ago
Nicely done! I'm wondering if an armature would be overkill?
huplescat (author)  tomascco10 days ago
Probably :D
"guesstimate the amount needed"
Fill a vessel with water (to the brim). Stick your hand into the container, catch the spill over in another container. Pour the 'spill over' into a measuring cup (or some such) and you will have the volume (of plaster) required. Its fizzicks!
thayray14 days ago
You have man's hands? Weren't you on Seinfeld once? :D
seamster25 days ago
Well done! I let out a gasp when I saw the broken fingers. We've all been there - after so much work and something goes wrong! Nice to see that it was an easy enough fix though, and the finished hand cast looks great! : )
huplescat (author)  seamster25 days ago
Ugh yes, my heart sank when I saw it on the ground! But I guess part of making things is rolling with the disasters :)

And thanks!
M3G25 days ago
Nice work! I love your writing style, this was an entertaining read.
huplescat (author)  M3G25 days ago
Thank you :)