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Making Slumping Molds from Clay

 

This is part two of a multi-part tip on making slumping molds from clay.  Click here to start with part one.

 

Although there are many kinds of clay that can be used for mold-making, these two choices tend to have the best combination of durability, kiln wash compatibility,  and resistance to thermal shock.

 

1.  Raku clay

 

Just about any clay can be made into a raku clay by adding sand. The purpose of the sand is to minimize the risk of thermal shock during raku firings (which involves removing the clay from a hot kiln and causing the glaze to crack due to the sudden change in temperature).  Although you can make raku clay yourself from any ordinary clay by wedging sand into the body of the clay, it's far easier to just buy a raku clay from a pottery supplier. 

 

2.  Paper clay

 

A relatively recent development, paper clay has several advantages over standard ceramic clays.  It's made by mixing paper pulp into clay; the resulting product is light weight and exceptionally strong.  Unlike regular clay,  which can not be altered once it dries, it's possible to modify or even add on to dried paper clay.  Cracks can even be repaired in dry paper clay, making it much more forgiving than regular clay.  Since it's labor intensive to make paper clay, it's best to buy it already made.  It's carried by most large pottery suppliers, such as Axner.

 

Regardless of which clay you select, it's often a good idea to specify white earthenware (rather than brown earthenware) to avoid the possibility of stains that colored clays can create.

 

 

Click here for part three of this tip, which will focus on the materials needed for making the slump mold form.

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Copyright 2006 Brad Walker.  All rights reserved.

Special thanks to Leslie Ihde for her assistance with this writeup.

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Copyright 2005-2006 by M. Bradley Walker.  All rights reserved.

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