POST – Columns of refractory material used to support shelves in the kiln. They are available
with square, triangular, or circular cross sections and in many different heights.
PYROMETER – A high temperature thermometer consisting of a heat sensing device
(thermocouple) connected to a meter readout. Especially important in working with glass. This is
an excellent device to measure the progress of a firing and temperature profile of a kiln.
PYROMETRIC CONE – A small elongated pyramid of ceramic material which his formulated
to soften and deform at a specific temperature plus time condition, indicating that the ware is
mature and the firing complete.
SHELVES – Slab of refractory material used in the kiln to support ware being fired (see
furniture)
SILICA – (SILICAFLOUR, FLINT) A mineral powder used to prevent sticking of porcelain and
other high fire clays during firing.
SLIP – Liquid clay used in casting shapes with molds.
SOAKING – Heat treating objects in a kiln by keeping them at a particular temperature for a
period of time.
STILTS – Small ceramic or high temperature metal prongs used to raise a piece off the kiln shelf.
Used chiefly in glaze firings to prevent sticking to the kiln or shelf. Many styles are available.
STONEWARE – A ceramic body which is vitreous but not translucent when high fired. It
usually contains a high percentage of grog (fired clay particles) and is usually made of native
clays.
TERRA COTTA – A natural, low fire red clay.
THERMAL SHOCK – The result of putting ware through sudden changes in temperature.
THERMOCOUPLE – Two wires of different metals which are inserted into the kiln and
comprise the temperature sensing part of the pyrometer. It produces a very small voltage in
proportion to the difference in temperature between the tip (hot junction) of the thermocouple
inside the hot kiln and the cold junction on the outside of the kiln.
UNDERGLAZE – Decorative material applied to green ware or bisque.
VENTING – Allowing air into the kiln and vapors to escape by propping the lid slightly open
and sometimes opening the peepholes. Usually done only in the early stages of firing.
VITRIFY – To fully fuse ceramic material to a glass-like state so that it is nonporous and
watertight without glazing.
WARE – General term for any shaped ceramic object whether or not it is in a finished state.
WARPAGE – Deformation of ware during firing, usually due to over firing or to improper
placement in the kiln.
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