I am going to be making some puppets, which will essentially be talking shapes. So they will not have the usual facial structure. The mouths would slashed into the silicone.
We were thinking of painting a silicone skin into a hard mould and then filling with an expanding foam. There will be some wire and a core running through as we want them to be able to bend a bit.
Has anybody done anything similar? I am wondering what type of silicone would be best for getting the right flexibilty, and how it would work with expanding foam. Are there any potential problems to look out for?
We will pigment the silicone and paint afterwards too, so if anyone could advise on this that would be great.
I haven't tried silicone and expanding foam, but I don't see why it wouldn't work. Latex and foam work very nicely when done in this way, and the foam sticks to the latex with no problem.
I suspect it might not adhere to the silicone, so some form of mechanical bond might be needed. Although you can easily test for whether the two materials bond with a little blob and some foam. What would work as a mechanical bond? Adding some bits of physio wrap into the final layer of silicone might be one way, but might compromise the flexibility of the silicone a bit. Alternatively, perhaps lifting the silicone skin off the foam on the finished piece and using some silicone to stick it back down again might be the way. For sticking silicone I like to use neutral cure glazing type silicone available from builders merchants. Dow Corning 791 is an example. This has the advantage of being a thick consistency, and it comes in transparent.
The silicone I use for skins is Plat-Sil Gel 00, or Gel 10 for a slightly tougher skin. Probably the latter would be best choice here. It goes off quickly, so is ideal for layering into a mould, and can have some thickener added to make it a bit more gloopy.
For pigmenting, there are some great skin tone pigments available from people who sell silicone for prosthetic make-up, and you can buy sample selections of Silc-Pig, little pots in about ten colours, so quantities small enough for puppets!
On the colouring afterwards, the way to go is to use the Dow Corning thinned with either naptha or d-limonene. The latter is much less hazardous and smells of orange peel. But it also retards the silicone, so layers have to be done over quite a long time. Use the pigments as above, and dust with icing sugar to matt the finish. This can then be washed off once the silicone is set.
You can also use the Plat-sil thinned as above for painting.
There is an expanding silicone foam that can be used to fill a silicone skin. I believe it does bond to the platinum silicone. I could have used it for a Sumo wrestler, to reduce the weight, only it isn't sold in my country so I haven't tried it myself. Ron Cole has used it. It is called Soma Foama, made by Smooth-On. https://www.smooth-on.com/product-line/soma-foama/
I've worked with two types of silicone foam--Soma Foama from Smooth-On and a product called Silpak 2000. Soma Foama has a lot of expansion and the Silpak product has a little less. They can expand more or less depending on their temperature. I haven't figured out a good way to estimate a really accurate amount for each part of my Ultracal 30 molds. So I cast the armature in the foam, first on one side and then on the other. Then I trim the foam so it fits the mold. Finally I paint in a Dragon Skin FX pro skin in a couple steps and set the foam covered armature inside before the silicone skin completely sets up. This is not as light as with either a latex build up puppet with cushion foam or a foam latex puppet. My puppets are, however, significantly lighter than if you cast a solid platinum silicone puppet.
Thanks everyone!!!! This is really helpful. We've ordered some materials now so we can start testing.