Just recently in my sculpture class in college, I have made my first slip cast mould. I have looked at the type of plaster used and it was pottery plaster. So I was wondering if that kind of plaster can work for casting puppets or are there other kinds of plaster you guys recommend.
The one usually recommended is Ultracal 30, a harder, denser plaster.
Hydrostone is also very good - not sure, it might come from the UK.
For slip casting with liquid latex, I used to use ordinary casting plaster, and it works ok, even though the surface isn't as hard. I think pottery plaster would be similar - I would imagine it's made mostly for slip casting with clay. I haven't actually used it. Casting plaster can be used for foam latex if you only want 2 or 3 casts, but the surface does start to break down after being baked in the oven a few times. If you have a highly detailed surface, the stronger plasters are much better, as little bits can break off with the cheaper plasters.
Ultracal used to cost 10 times as much as casting plaster here (in Australia), if you could even find it. It's made in the US. It's only about 5 times as much now, the locally made casting plaster has become more expensive. My usual method is to use Hydrostone or Ultracal for the first 2 layers of the mould, then a mix of whatever Hydrostone is left with some ordinary casting plaster and some chopped strand fibreglass matting or loose weave hessian for reinforcment, then just the casting plaster and fibreglass to build up the thickness. That gives me a hard surface where it counts, but saves money. These hybrid plaster moulds seem to stand up to dozens of casts and baking in the oven, and can be stored for decades.