[HDTVinc]

Hello all,

I am an undergraduate who is looking to be able to synthesize a very soft, very stretchy silicon rubber. I would really like to be able to make a moldible silicon rubber, but I cannot find any information on making this sort of thing anywhere.
Ideally, it would be a two part system where you mix A and B together and it cures within 24-48 hours.

does anyone have any idea where I could go about getting inforamtion on creating this myself in stead of spending TONS of money on comercial products like it?

below is an example of the type of product i am looking for:
http://www.fxwarehouse.info/product/Plat10-0.html

[Enthalpy]

That's the usual price for such silicones, including for other uses and in bigger amounts, despite several manufacturers compete.

Could you perhaps consider other materials like gelatine?

Natural rubber can also be applied as a solution in several layers with a brush. Used for sex games, expectedly cheaper over other channels if it has other uses. I've no idea whether it's available cheaper than silicone rubber. Natural rubber can be very soft: vulcanisation makes it harder in usual items.

Other elastomers are naturally harder.

[HDTVinc]

I have been doing some research, and I came across a guy who says that he thought that silicone caulk could be diluted to give a similar end result that could be sprayed onto a surface via an airbrush, so I may look into doing a few experiments to see if this is possible. He also suggested that a few different additives like corn starch would aid in speeding up the curing process, as well as improve on its elastic qualities once it has fully cured.

Thank you very much for your input, it is your post about natural rubber that got the ball rolling!

[Intanjir]

I Googled "stretchy caulk". Big Stretch Caulk claims something like 5x elongation. It advertises itself as "acrylic latex" so not silicone, but no doubt rubbery. The 'latex' is presumably just lingo for hydrophilic solvent, so you might try diluting it with an alcohol if you attempt to make a paintable version.

Oh I just found that there are also "elastomeric paints" with similar elongation capacity and chemistry.

[HDTVinc]

Another person has suggested that I may be able to dilute the silicone caulk with a silicone oil, but i am not sure if it would make it bad for prolonged skin exposure. Ideally I would like to use a material that will not irritate the skin. I have done a bit of research, and if it does properly mix together, this should allow for a softening of the silicone that will better emulate skin. It should also allow for the final product to be a bit translucent, so that is a plus. The application of the silicone would be mostly for FX makeup, masks, and prosthetic, so it will need to be safe on skin.

Any thoughts?

[Intanjir]

I'm not sure what effect adding silicone oil would have. I think it would not participate in the cure as its ends are presumably already capped with methyls. However if it is long enough and mixed thoroughly in before the cure then it should become entangled with all the rest. I would guess the result would at least be softer than the normal caulk.
Silly Putty and boric acid would also be interesting things to try with caulk. Though you'd probably have to make triethylborate or similar to get the boric acid in.

[Enthalpy]

Adding silicone oil prior to curing is a known method to make silicone rubbers softer - with no clear limit. No idea what happens to the molecules then, but for the user it has some merit. I don't quite remember all the possible paths of silicone curing; the reactions are quite varied.

This would bring a softer cured silicone rubber, but it wouldn't reduce the cost, since oil is about as expensive.

Wacker had nice documentation about silicone rubbers and oils a decade ago. Worth reading it.

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I had already samples of ultra-soft gels. They were amazing. Is there a means to pour and cure such things in a mold?

[HDTVinc]

With the silicone caulking, the reaction uses water from the air in order to cure. So if you add something that will provide the water to the reaction, then it should be able to cure in a mold, though it may take longer to do so. I have been told that adding Latex paint in small quantities and stirring until a consistant color persists speeds up the process.

I am thinking that I can add the silicone oil and latex paint to the caulking in order to dilute it down enough to be able to pour it into a pre-made mold. If I can get it to cure, with a fairly high level of softness, a high level of stretch, and have no ill effects when it is placed against the skin for an extended period of time, then my project will be complete!

As far as the price of silicone oil goes, it will still be more affordable over commercial platinum silicone and even tin based silicone products that are on the market now.

Thank you all very much for your input, it is helping a lot!

[Intanjir]

How would you mix the hydrophilic latex paint into an oil?

They commonly cure in part by taking water from the air to slowly hydrolyze something like methyltriacetoxysilane. The resulting -OH groups are then available to condensate with one another forming permanent Si-O-Si bridges. I suspect that if you were to directly add more than a low concentration of water then the reaction would happen impractically quickly.

So anything water-based will probably instantly cure, ie faster than you can stir, and anything substantially hydrophilic just isn't going to mix properly.
It might work though if the paint has a very low water content with an amphiphilic solvent.
Or maybe it does work and it works just because it mixes poorly so the water is initially confined in tiny droplets of a separate phase.

[HDTVinc]

Only a few drops of latex paint is added to the mix. I would only be able to speculate as to why it helps the curing process, but it is a common issue when using silicone caulk that thicker layers cure very slowly. If you make it too thick, then the outside edges cure much quicker than the center causing the inner most portion of the cast to remain liquid because it is completely cut off from the moisture in the atmosphere. The paint either, adds just enough moisture to make thicker portions cure, or makes the silicone porous enough to counteract the effect of the outer layers completely sealing off the inner layer.

The idea is that I would cast an entire mask of limb from the stuff, which would require a fairly thick layer of silicone. I have spoken with a few people who have played with this idea in the past, but none of them tried using silicone oil. I will hopefully be able to get my hands on all of the materials needed so I can make a few blends of various materials at various quantities in order to determine what mixture cures at a reasonable rate, yields the stretchiest/strongest material, and has minimal shrinkage.

I am really hoping that it works out!

I am also planning to do one mixture without any latex paint, because I am hoping that adding silicone oil will be enough. If it makes it thin enough to put through an air brush then I will consider it a great success.