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  1. I'm a ceramic newbie with a question: can the heat produced by curing plaster cause oil from oil-based clay to leech into the walls of a two-part plaster mold? I've been making simple two-part molds and casting solid plaster objects wqithout problems. Now, I'm experimenting with making two-part molds for slip casting with Liquache, a liquid paper mache product and AM experiencing problems. Something in the mold-making process appears to be affecting the absorption qualities of the plaster molds. It occurred to me that the same oil-based clays which work fine for making molds and casting solid plaster objects may not work as well for molds intended for slip casting where water must pass out of the slip and into the plaster walls. The problem I'm having suggests that parts of the mold aren't allowing an even absorption of that water. So question 1: Is oil-based clay appropriate to use in the process of making plaster mold for slip castings, i.e., is its oil-content a problem? and Question 2: What kind or brand of non-oil-based clay might best be used for this purpose?