Making small molds for casting part 2

Notice that I dropped plaster as a material I use with molds. Last week I went to Jerry's Artarama and got an 8 lb box of white sculpey ($32.00-much better buy than the 1 lb box) and I've been using this in molds with great results. Do NOT mix the softener with it...just use it as it comes out of the box. I've experimented all week and learned lots more.

Silicone caulk; the fast drying caulk (the kind you use the giant squirt gun thing with) leaves lots of air holes, cracks fast but also dries FAST. The tubed caulk (Elmers Squeez'n caulk and Loctite tub and tile ultra sealant-clear) worked the best and have not cracked from multiple casts.You can use this caulk for the first layer of the mold. I've been using veg oil on the matrix to ease the mold off.  The silicone giant squirt gun kind is good to build up the backs of the thinner, slower drying first caulk molds.

After trying oil (messy) and alcohol (ditto) I came upon an online article mentioning plain old talc powder as a mold release. This is just perfect and I've been getting great mold castings. (sorry for the poor photos-I'm in need of a better camera)

So, I'm using Sculpey to make the molds with a talc release.I dust the mold with the powder, then push a small kneaded ball of Sculpey into the mold until I feel sure the details are picked up.

Then I flip it sculpey side down on the enamel butcher's tray and push from the outside of the mold to make the back somewhat flat. This also makes the casting stick to the enamel.

Carefully I lift up the silicone mold (flexibility of the mold is what makes this so much easier) and you will have a good casting.

You can make multiple molds like these skulls and cast them together or apart;

Then it's time to bake. I was lucky to find a thrift store Black and Decker toaster oven with a timer and thermostat. Remember, you're not going to ever use this for food so if it's a yucky, used one it doesn't matter.

Line the pan with alum foil and use the scraper tool or a metal spatula to place (similar thickness) pieces on the pan. Then tent them with more foil to guard against burning. Even so, some will burn but I'm going to paint these in the end it's no matter.

The fan is directing any fumes out the sliding door...

Note my muse...also note that I don't let him in the room while baking Sculpey. His lungs are tiny and it wouldn't take many fumes to irritate him. He just supervises before and after. If you have a cat, keep it out of the baking room as well. My oven has a timer bell which is really nice.

Once the timer goes off I wait several minutes for them to completely cool inside the oven. I think this helps the curing process inside. See what I mean about burning? There's no distortion of the image so it's ok.
To check that they are cooked and cured I press a fingernail into the back. If no mark is left they're good to go. I've used E-6000 glue to attach them to unpainted plaster and it's a good hold. Hope this saves you a little time with your mold making adventures!