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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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