The
First Firing of a Ceramic piece
After being molded, dried, cleaned and under glazed the
piece is ready to undergo its first firing. The prepared
or under glazed piece is now set inside a kiln to begin
the process.
During this first phase, a low temperature
of 100 °F to 300 °F is attained. At these temperatures,
water is physically removed and vapors are released. This
is considered the warming phase. Depending on the size of
the ware as well as it's weight and it's thickness, it will
require a longer warming period. This prepares the piece
for the next phase.
The 2nd phase or “preheat”
phase is then completed using medium heat , followed by
the third phase using high temperatures or full heat, where
temperatures of 500 °F – 1300 °F are reached.
At this stage impurities and organic matter burn out of
the clay. Chemically released gases and water are also given
off. At 660°F greenware changes to bisque. At this stage
the piece is still quite fragile, but water can no longer
return the piece to a lump of clay.
At 1000 °F, something referred to as
quartz inversion occurs. This means the crystal structure
of the quartz in the clay piece is changed. It is at this
point that the ware is under the most stress. When the piece
is finished firing it is allowed sufficient time to cool.
Phase one - Warming :
1 - 3 hours on low.
Phase two - Preheat : 2 - 4 hours on medium.
Phase three - Full heat : 2 - 4 hours on
high.
This completes the process of firing raw
material (greenware) to create bisque. Cooling times can
range from 8 -16 hours before being removed from the kiln.
The piece is now ready for decoration and further firings.
For more information please visit the
"Second Firing" link on the left.
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