material for flexible "inner moulds"

[sue williams]

I am making small (12" high") intricate sculptures in plaster and would like to slip cast them into clay. Thay are too complex and 3-D for multiple piece plaster moulds so I'm searching for a material with which to make flexible INNER MOULDS (supported by plaster jackets). The material for the (peelable) inner moulds therefore needs to be FLEXIBLE, POROUS and able to be applied to the original in order to pick up all detail. Not a lot to ask I know but if I could find such a material it would open up exciting new possiblities. Thanks, Sue. (Newbie to this forum).

[grommet]

Sue,
You & me both. The porous part is the sticking point., really. The possible alternatives I've considered are:
1.Reducing undercuts so the piece can be plaster molded & making a thicker slip casting so the undercuts may be carved out again after unmolding. (How many pieces is too many?)
2.latex or silicone mold (with jacket / mother mold a/n) press clay into halves & reassemble (score & slip)
3. Latex & plaster mold, cast with "aqua-resin" including oxide colorants.

I went with #1, but wonder what other folks may have to contribute.
Good luck!

[Ironlady]

i'm a fan of silicon w/ a mother mold

[clonesix]

Slip casting requires a porous material like plaster to draw out the water. There lies the problem: porous + flexible. I do not know that such a material exists.

Does it need to be cast in ceramic? Could these be cast in resin?

I see only 2 alternatives:

1. reduce the undercuts in the piece in order to mold it in plaster.

2. change your medium to one that will work in a silicone mold.