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Homemade Mold Making Rubber

#1 2012-11-26 06:21:06

CatPerson
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From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Homemade Mold Making Rubber

It's hard to believe that you could mix gelatin, glucose (sugar), glycerin and a bit of alcohol and get a kind of rubber.  And the rubber, while moderately flexible, is very tough.  I've tried and I can't tear it.  And it's reusable by melting!

Sue



I tried this mold material and it is quite good, although it is sensitive to heat.  In fact, you can melt it down and re-use and reform it.  It feels like a very dense, foamy rubber, flexible, but quite sturdy. I tried to tear a simple mold and couldn't do it.  It appears infinitely reusable.

If you're going to start mixing this stuff, do it when you won't have any interruptions. Don't get sidetracked or you will regret it. (Trust me on this....)

And don't try to rush things and add all the ingredients at once, or add them in another order. I paid $16 for a gallon of glycerin through my vet & wasted quite a bit.

!!!DENATURED ALCOHOL IS A FUEL -- IT'S EXPLOSIVE!!! DO NOT ADD WHILE ON THE STOVE. DO NOT SMOKE WHILE USING. It is NOT rubbing alcohol. PAY ATTENTION!!!

RECIPE for large batch (smaller experimental batch at end of post)

4 1/2 pounds dry Gelatin (in flake, grainular or powder form) from a health food store.  This is the same stuff as plain Knox brand gelatin).  SMELL IT before you buy! If it smells like Jello, it's the right stuff.  Don't accept cornstarch -- some clerks don't know the difference.
9 cups of cool water (2.25 qts.)
13 cups Glycerin (3.25 qts or 9 lbs) (check with your veterinarian)
1 lb. glucose (a similar product is corn syrup-- use a 16 oz bottle)
1 oz. Denatured Alcohol (from hardware store)

Put the measured glycerin into a pot over LOW heat & start it heating. You do NOT add it to the gelatin unheated.

Pour the water into a large cooking pot & add the gelatin. Start mixing immediately & keep mixing until all the water & the gelatin are thoroughly mixed together (I used my hands). DON'T STOP mixing or it will separate & congeal in layers. When ready, the mess should be consistent in quality. If you do have to stop, cover the pot with a damp towel.

Place the pot of gelatin over LOW heat & start stirring when it begins to melt, and keep stirring until the gelatin is all melted and free from lumps. Then add the heated glycerin and stir until well blended. Then add the glucose and continue to mix until it is fully incorporated.

REMOVE AWAY FROM THE STOVE ENTIRELY. Now add the alcohol and stir until thoroughly blended with the rest of the mixture. It is now ready to use, & should be formed while warm.

NOTES:
Cooling the new mold can be accelerated by placing in the refrigerator.

I would tend to use dedicated utensils for this project.  Glycerin has fairly low toxicity (I still wouldn't eat it).  The denatured alcohol is the most toxic ingredient.  Everything else should be food grade.

The original recipe said to cook in a double boiler, but I didn't have one large enough, & didn't want to mess with 2 pots with rocks or marbles between, & just kept the temp on the lowest temp of my electric stove.

To make into another mold, just put back in the pot and heat at LOW temperature. DO NOT add water.

This material can be used many times. If it starts getting debris in it, just form a sieve made from wire window screening in a funnel shape and while the material is melted, pour it through into another container.

_____________________________
1/3 SIZED RECIPE FOR TRIAL -- it still makes quite a bit

1.5 lbs gelatin
3 cups cool water
4 1/3 cups glycerin
1/3 lb glucose (corn syrup is a good substitute - use 1/3 of a 16 oz bottle)
1 Tablespoon denatured alcohol
-

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#2 2012-11-26 14:49:58

bmaskmaker
Member
From: Takoma Park, MD
Registered: 2010-04-08
Posts: 93

Re: Homemade Mold Making Rubber

Very cool. 

I use something called Composimold ... and I wonder if that's basically how they make that product.  I'd be willing to take more risks with it with a homemade batch, tho.  : )

You could incorporate it into your other mold ideas.  Pour / brush on a thin layer of homemade rubber mold material.  Let dry.  Then add a more solid backing of pulp or strip mache.  Frankly I'm way too impatient, so tend to use plaster vs. mache.  But it could work. 

Also ... the composimold people have a bubble-buster product that you spray on your original to prevent air bubbles in your mold.  Air bubbles are my biggest complaint ... but if you did thin brush /pour mold, I wonder if you could see them and pin pop them before adding more mold material.  The material is transparent-ish ... no?

Great stuff to think about on a Monday morning.  : )

-- b

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#3 2012-11-26 18:16:17

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Re: Homemade Mold Making Rubber

Actually, no, it isn't transparent, and it comes out tan.  If you looked at the list of ingredients and looked at the 'rubber', you would never connect the two at all.

But using it as a mold liner might be something to consider.  If I can get going on my PM-as-a-mold (above), I could melt down one of the rubber pieces and coat it with it.

Sue

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#4 2012-11-26 18:39:29

mavigogun
Member
From: Istanbul
Registered: 2009-04-22
Posts: 106

Re: Homemade Mold Making Rubber

Bitchen!   -you rock, Sue.   Can you comment on the viscosity at pouring temperature? -relative to small inclusions, details?   Does the viscosity increase rapidly with only minor cooling- say, what might be imparted from a larger, room temperature model?

Thanx.

-Christopher

Last edited by mavigogun (2012-11-26 18:43:09)

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#5 2012-11-27 05:49:01

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Re: Homemade Mold Making Rubber

I don't know if small items would work, as what I've got has some bubble holes in it -- it's kind of foamy.

OTOH (and I hate to admit to this level of stupidity), HAD I ADDED THE GLUCOSE, it might have turned out differently.  I did the whole (small) batch and left out the glucose.  Totally forgot.  Still got the rubber, but the texture may have been different had I done it properly. *covering face with hands*

Maybe I can melt a section and add some glucose (now that I know where to find it) and see what happens.  Maybe it will cure the bubbles.

Sue

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#6 2012-12-02 18:05:56

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Re: Homemade Mold Making Rubber

When I just tried to buy glucose, no one seems to carry it except the big bakery ingredient sources.  Doing a bit of research, food-grade corn syrup is supposed to be close enough, so I tweaked the recipe.

Sue

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#7 2013-01-16 19:38:42

bmaskmaker
Member
From: Takoma Park, MD
Registered: 2010-04-08
Posts: 93

Re: Homemade Mold Making Rubber

Sue,

I have a small bottle of CVS brand glucose.  Must have bought in the last couple of years (no dust  : ) ) ... not sure if they sell larger bottles or not, but have you checked drug stores?

-- b

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#8 2013-01-16 20:26:01

CatPerson
Moderator
From: Washington State, U.S.A.
Registered: 2006-01-09
Posts: 1307

Re: Homemade Mold Making Rubber

Beth, I've come to the conclusion that the simplest form of glucose is corn syrup.  Before I send you that sample, I hope to try melting some of my supply down and adding some corn syrup, to see what effect it has. 

I haven't forgotten you, I'm just dragging my feet.

Sue

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