Page 20 - VRT PORCELAIN

Firing

● Firing is a further heating step that can be done in one of two
types of oven, or kiln. A periodic kiln consists of a single,

refractory-lined, sealed chamber with burner ports and flues.. It
can fire only one batch of ware at a time.

● During the firing process, a variety of reactions take place.
First, carbon-based impurities burn out, chemical water evolves
and carbonates and sulfates begin to decompose.

● On further heating, some of the minerals break down into
other phases and the fluxes present (feldspar and flint) react
with the decomposing minerals to form liquid glasses. These glass

phases are necessary for shrinking and bonding the grains.

● After the desired density is achieved, the ware is cooled,
which causes the liquid glass to solidify, thereby forming a
strong bond between the remaining crystalline grains. After
cooling, the porcelain is complete.