porcelain slip cast into 4 part rubber mould

[JoanH]

Hi, has anyone slip cast into 4 part rubber mould, is it even possible?

[Denice]

You would probably end up with a moldy mess by the time the slip dried enough to pop out of the mold.  The plaster mold absorbs the moisture out of the slip, it would take months for the slip to evaporate in a rubber mold.      Denice

[neilestrick]

You need a plaster mold for casting slip. The plaster absorbs the water from the slip so it can become firm enough to remove from the mold. In a rubber mold, it would never dry properly.

[liambesaw]

You could cast plaster into the rubber mold, then make a 4 part plaster mold of the plaster casting, and then use it to slip cast.  

[Mark C.]

Rubber molds often called master molds are for making waking molds from Plaster. 

I have made many a working mold from a 4 piece rubber mold. You do not use slip clay but plaster in a rubber mold.Then once you have a plaster mold you can slip cast in that.

[Rae Reich]

You could try packing a layer of firm clay into the talc-dusted mold or mold parts , unmolding as soon as possible to join and dry, if you just want a one-off piece. The rubber will not allow the clay to dry, but might be flexible enough to peel from the clay. Expect distortion which might be repairable because the clay is still damp. 

[Chilly]

What they said above.  All points covered.