Oil-based Clay, plaster and heat
Posted 17 May 2012 - 12:54 PM
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?
Posted 17 May 2012 - 01:26 PM
A good oil based clay is Sculpture House Roma Plastilina Sulphur free; available in four consistencies hard, medium hard, medium and soft.
Posted 17 May 2012 - 01:51 PM
i was taught to make plaster molds with just regular ceramics clay object or found object. use same clay body for imbedding @ midpoint or section. quick coddles made from either clay, vinyl, or tar paper. pure lube mold soap for release agent. pottery plaster #1 as the plaster. when the mold's released, do a quick wash/wipe out with vinegar to remove mold soap, then dry mold while strapped together.
Posted 17 May 2012 - 03:11 PM
Kiln Repair Tech
Owner, Neil Estrick Gallery, LLC
Posted 17 May 2012 - 06:00 PM
Head of Ceramics, Central Washington University
CWU offers; BA, BFA, and MFA Degrees, (Post Baccalaureate also available). Images of CWU Ceramics studio can be seen at
Posted 18 May 2012 - 08:45 AM
Posted 18 May 2012 - 07:03 PM
I agree with Denice. I sometimes scrub my molds with a soft bristle tooth brush or a cellulose sponge.
If necessary wash the mold with a diluted mix of Dawn and hot water. I recommend saturating your mold with plain water prior to using the Dawn to prevent the mold from getting soapy.
Posted 20 May 2012 - 11:44 AM