I recently made this post about some commercials:
The client would like to have this puppet standing in the shop. So I proposed to make a painted (ultracal 30) cast out of it.
I wanted to know if anybody here has experience with casting plasticine models. The model will be standing up straight with it's hands holding a guitar (I will add the guitar later, not part of the cast).
I think it needs a two part mold for sure, but then I wonder how to make the barrier around the model and between the arms, because the model itself is already in plasticine. I could pour one half and then the other. But then I can't make keys in the silicone and then I can't choose where each half begins.
To make just one copy, I usually make the mould from alginate. I make the clay wall from water based clay. Alginate is a powder that you mix with water. It sets very quickly. It is usually used by dentists for making moulds of your teeth, and is also good for face moulds. The drawback is that it is often damaged taking out the first plaster cast, and will soon start drying out and shrinking even if you do get the first cast out. It needs a bit of support, so I make a plaster Case Mould (also called Mother Mould) for the outside, to support it.
This bust is plaster, cast in an alginate mould, from a plasticine original:
When I make 2 piece a mould from polyester resin, which does not set if it is in contact with moisture, I do use a plasticine clay wall. But first I give the plasticine sculpt a coating of shellac, and then I use a softer plasticine like Klean Clay, for the wall. Klean Clay is sulphur free, so would be fine for making a silicone mould with any type of silicone.
This shows a sculpt made in Chavant NSP medium, coated with shellac, and a clay wall being built up with Klean Clay. As I said, in this case the mould was made from fibreglass since I was going to be casting is silicone, but if it were made with the figure lying down, and a box around the outside, you could make a silicone mould from this.
I would like send you a private message but I can't if you don't accept my friend invite :)
Thank you Nick!
Because I already have the silicone, I will be using that for the mould.
Can you compare shellac with varnish? Or does it work differently?
I would like to be able to animate/use the puppet after the cast. So maybe I'll just use the softer plasticine wall as you said, which won't stick to the plasticine puppet that much.
Or, I can use the shellac and redo the top plasticine layer of the puppet after the cast. What would be best you think?
Hi. I started a very similar topic:
However I would like some advice as to what I can use to make the mold walls. I am using Plaster of Paris (as this is my first attempt at casting) on a Plasticine sculpt.
Thank you, Nick!
This was my first plaster cast. I like the way it cures so fast and that it's easy to work on afterwards.
Nice work Maarten. I saw this post a while ago and just looked at your final cast update tonight. looks great.