Silicone Rubber Sculpture Techniques

Silicone rubber is not a common sculpture material.  It is sticky, puts off ascetic acid fumes as it cures, and you can't use your bare hands to work with it.  This instructable is about various uncommon techniques I have developed to work with it. 

Silicone rubber is normally used as a sealant for windows, etc.  You can buy it in 10.5 fl. oz. grease gun cartridges at a hardware store for around $4, so it is not prohibitively expensive to work with.  It comes in a limited variety of colors, such as black, white, brown and clear.  I always buy clear silicone and colorize it myself with powdered pigments. 

You can get some cheap powdered pigments that are used for colorizing cement at some hardware stores.  A wider range of colors can be obtained from some art supply dealers.  (Google search "artist powder pigments" for some online sources.)

Here you will find photos of some of my silicone rubber sculptures and brief explanations of how they were made.  Most of the sculptures were built up directly.  Others were made indirectly, using molds.  The belly dancer below was a complicated piece made with several molds.  I will explain it in more detail later. 

Step 1 Silicone Rubber

I don't know the ecological side effects of manufacturing silicone rubber, or its eventual decomposition.  When cured, it is non-toxic.  It comes out of the cartridge as a sticky paste, smelling of ascetic acid (vinegar), and it cures fairly quickly, turning into a rubbery substance. 

It sticks like crazy to some non-porous materials, like glass, metal, and more silicone rubber.  It doesn't stick well to other materials, like wood and some plastics.  My preferred work surface is polyethylene plastic, because the silicone peels right off of it when it hardens.  Plastic trash bags are polyethylene plastic and can be stretched out over a board or table as a work surface.  I bought some thicker polyethylene years ago that didn't need stretching.  Recently, I found thick polyethylene plastic kitchen cutting board, which I plan to use as a work surface in the future. 

If you get it on your skin, wipe it off right away.  It is not immediately aggressive, but skin contact for too long can cause your skin to peel. 

Silicone rubber has very good longevity.  As a sealer, it is guaranteed outdoors for 30 years.  An indoors sculpture should easily last a lifetime. 

Comments

[a_lil_monkey]

Very interesting..

I wonder if you could color the silicone with powdered eye make up. They come in small tubs; but maybe for a special color. : )

[Thinkenstein]

Nice idea. Worth a try. Any powdered pigment should work. Dick Blick art supplies also carries a good selection of powdered pigments.

[blluntman_exe]

I really enjoyed this piece, until I read it I thought I was the only one who has bothered to use silicone as a modelling material. I've used it primarily for utilitarian things like fixing a broom handle and for a custom made water proof light fixture.

However I've also used it for a custom drawing mannequin, it was made using a metal armature with rigid material forming the bones and silicone layered on top to form the fleshy outer layers.

One useful method I've found that keeps silicone modelling a little less messy is to use cling wrap plastic around the roughly applied silicone and then the silicone can be shaped and smoothed with out mess. And once the silicone is cured the cling wrap peels off easily.

Oh and I have conceived a moulding technique that I will test soon. It involves a peculiar interaction between water and silicone. I've found that water has a habit of getting between silicone and what it's trying to bond with. I believe this has the potential to become a replacement release agent. I plan to test it by making a 2-3 part silicone mould (fully cured), then to inject silicone into the mould and then immerse that into a body water. If it works I'll be sure to let ya know.

[Thinkenstein]

I like your drawing mannequin and plastic wrap technique for smooth surfaces. I got a polyethylene kitchen cutting board at Sam's Club which I use as a non-stick work surface. It's good for making flat, smooth sheets of silicone.

Good luck with the water test.

[kirnex]

There are a few grades of silicone; in the question of toxicity, breaking it down to food-grade vs. non-food grade is most adequate (food-grade items will definitely specify this). Additionally, silicone also comes in a number of heat-tolerant types: the grade used for home-type trimming and finishing is low-heat tolerant, while various other grades of silicone (a.k.a the silicone non-stick sheet you used, Thinkenstein) can withstand temperatures of up to 450-500 degrees. Ahhhhh, the wonders of science. Just bring this latter point up for those of us wanting a grade that can handle heated mixtures.

I've had amazing success with dental grade almalgamates (an obvious food-safe alternative to silicone), but am currently finding myself frustrated with a new agent: food-safe, gelatin-based alginates. Specifically, I find that they don't set up well for me: I get too much water run-off and even if I use cardboard for my reinforced vessle, I end up with lots of run-off that is difficult to reconcile without compromising the integrity of the form. That said, I am thinking of adding in generic unflavored gelatin to the mix and see where it takes me. It's a tricky science, these food-safe alginates (or maybe I'm just the idiot that can't get it!), but at a ratio of 1-part powder to 7-parts water, it's about the most cost-effective way to make molds, I've found. Just something to keep in mind if looking for a food-safe mold-building agent. :)

[Thinkenstein]

Thanks, Kirnex. That's interesting information about the silicone and mold making materials. I haven't used alginate mold material. I'll have to ask my dentist for some to play with.

[Dream Dragon]

That's all very interesting, I'd like to see more of your "bronze powder" technique.. I've read that two part Silicone comes in two varieties, "Tin Cure" and "Platinum Cure" and the only ONE of these is sufficiently non-toxic to be "food safe". Where does this kind of Silicone fit and could you use it for things that would come into contact with food?

[Thinkenstein]

I used a self-made silicone rubber non-stick sheet years ago to bake bread on in my microwave oven. I never got sick from it. Other than that, I am no expert on the subject of silicone and food safety. It lasts at least 30 years outdoors, so it must not be discharging much material, if any under those weather conditions. It doesn't dissolve in acetone or lacquer thinner, or water for that matter, so I doubt it would dissolve in saliva. Anyway, I doubt it is a great health risk.

I'm not familiar with the two part varieties. I know something similar is used for making flexible molds.