Here are a few pictures of my plaster mold making experience.
This is my first plaster mold attempt. You can see my wooden coddle. I also use plastruct sheet between the plaster and the coddle to protect it. This is when I noticed polymer clay leaves a sticky residue so I switched to an oil-based clay.
Now you can see the first half of the body plaster mold with the build-up removed. Looks good.
Above you can see a failed attempt. I used liquid soap mixed with water as the mold release, but I didn't get it right. I now use Murphy Oil Soap mixed 50/50 with water which works. I thought I would have to start from scratch with this failed attempt, but I was told I can just clean one of the halves up, add keys, and then remake the other half of the mold. So that is what I did.
The mold release I used worked perfect this time, but I failed to mix the proper amount of plaster into the cup. I was able to add the additional powder needed, but it added more air bubbles into the mix. Since by this time I was panicking that the plaster will firm up too much before I can pour it I skipped the step of brushing plaster onto the figure... which resulted in air bubbles. There are only a few bubbles in the lower part of the body, so there is no point redoing it. But the head has enough air bubbles in the detailed area to require me to remake the mold. Also, I was impatient removing the head mold so there are blemishes on the top of the head.