Ancam

I need some technical help. I use Valentine’s casting slips. My moulds are very complicated (38 pieces) and their shapes somewhat restricts the shrinking of the cast. My casts are thin for lighting translucency. My moulds are at two scales, one takes 1.5l the larger 12l. The larger mould in particular has highlighted some problems: Glacier porcelain slip works well and I can leave the cast in the mould for 12 hours before demoulding. You can tell that there is some plasticity in the cast that allows a bit of flexibility in the body on demoulding without it cracking. Bone China and Parian however are much more tricky to succeed with and often result in multiple cracks that I repair with mixed success. After just 4 hours the cast will crack all on its own before I’ve even attempted demoulding. And demoulding causes so many cracks as the cast it brittle. What can I add to the Bone China and Parian slips to make them behave more like my Glacier Porcelain slip? Tony on a Digital fire post mentions adding 0.5% bentonite. I need to test but has anyone got any suggestions or input before I start messing with these pre made slips. many thanks. Anna