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POTTERY OF THE ISLAMIC PERIOD ON THE
KARAK PLATEAU Glossary of technical
terms For further details, see Orton, Tyer
and Vince (1993); Rice (1987); and Henderson (2000).
Clay: Clays are formed by the weathering and
decomposition of rocks.
The qualities of a given clay are defined by the types of rocks
from which it is derived and the secondary deposition of small
mineral inclusions. Clays can absorb water and thus become
plastic (i.e. easily malleable). For this reason, they have been
employed since the most ancient times for the manufacture of
vessels and other objects. Firing:
in order to make a clay vessel or artefact functional it needs
to be fired. For most pottery the firing is done in a kiln
(firing temperatures in different kilns may vary between
approximately 800-1300ºC), although Middle Islamic handmade
pottery appears to have been baked at a lower temperature in an
open fire or a covered fire (also known as a clamp).
Glaze: a thin, glassy coating on a ceramic vessel
made through the vitrification of silica-based (often in the
form of quartz or sand) layer added prior to firing. The
temperature at which the silica vitrifies (i.e. becomes
partially liquid) can be lowered through the use of a flux added
to the silica mixture. Common fluxes in this period include lead
compounds (to create ‘lead glazes’) or alkaline compounds formed
from the ashes of specific desert plants (to create ‘alkaline
glazes’). Handmade: the practice
of forming a vessel by hand, without the use of a kick wheel.
Commonly, a strip of clay is coiled into the approximate shape
and then smoothed and molded to the desired profile. Handmade
bowls are sometimes formed over a basket and handmade jugs
around a sack filled with sand or earth.
Kiln furniture: ceramic objects used to separate
vessels fired in a kiln. Commonly, these take the form of
ceramic rods, flat plates, and three-legged spacers (also known
as tripods or trivets). The presence of kiln furniture on a site
is an indication that pottery was manufactured nearby.
Levigation: before clays can be used by the
potter, they need to be prepared. This involves drying, crushing
and sieving the clay. The other important process is levigation
where the clay is placed with water into separating ponds. The
larger impurities settle off leaving the fine clay particles in
suspension with the water. Relief-molded:
objects such as lamps were commonly formed by pressing clay into
decorative molds. These molds might be made from baked clay or
plaster. Sherd: a broken piece
of a vessel. The vast majority of the ceramic vessels and
artefacts recovered from excavations and field surveys are
incomplete or fragmentary. Slip:
a fine clay in a liquid form that can be painted onto the
surface of an unglazed vessel. A slip may be added before the
application of a glaze. Alternatively, slips of different colors
can be used to decorate the surface of an unglazed vessel.
Stonepaste: an artificial clay made from a mixture
of ground quartz, ground glass, fine white clay. The resulting
paste tends to be white, somewhat brittle, with a granular
texture (also known as frit-ware or faience).\
Temper: mineral or organic substances added to a
clay in order to make it easier to shape or to reduce the
likelihood that it will crack during firing.
Ware: a term used by archaeologists to describe a
group of vessels or sherds exhibiting a set of common technical
and aesthetic characteristics. Waster:
a ceramic vessel that has broken or deformed during the firing
process. Excavated wasters are important to archaeologists
because such broken objects provide evidence that pottery was
produced in the immediate vicinity of the find.
Wheel thrown: the practice of forming a vessel on
a kick wheel. |
