Jonathan Kaplan on thu 30 jan 97
The following is taken from "Out of the Earth and into The Fire by Mimi
Obstler. (BTW this book is essential for any potter's library)
"Talc forms the mineral enstatite at the low temperature of earthenware
bodies. This material has a high thermal expansion and contraction rate
which causes the glaze to be put into compression upon coolin and thus
helps to eliminate crazing. Talc reduces the post fired moisture expansion
of the often pourous earthenware clay bodies and thus significantly
decreases the amount of moisture induced body expansion which produces
delayed crazing. ......."
"Talc increases thermal shock resistance of high temperature claybodies by
the production of cordierite and mullite materials....."
As a side bar, cordierite materials are significantly used in the
production of kiln furniture both domestically as well as foreign, and the
use of this furniture is quite useful in fast fire kilns.
Jonathan
Jonathan Kaplan
Ceramic Design Group Ltd./Production Services
PO Box 775112
Steamboat Springs CO 80477
jonathan@csn.net
(970) 879-9139*voice and fax
http://www.craftweb.com/org/jkaplan/cdg.shtml
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