Welcome to Ceramics Tips

Inert Material

Inert material: Material which is
passively resistant to any change. In
ceramics, we particularly refer to
materials which are relatively unaffected
by the action of heat or water.

Bentonite

Bentonite: A highly plastic collodial
clay-like material which is a useful
plasticiser and suspender

Ball clay

Glossery of Pottery Terms

Ball clay: A plastic secondary clay,
usually quite refractory, and firing to a
fairly pale, off-white colour.

Refractory

Refractory: Resistant to high temperatures.

Ceramic Change

Ceramic change: The point at which
chemically combined water is driven off
from clay molecules, so that the clay
becomes pot, and can no longer be
slaked down. This change is permanent
and irreversible, and is widely said to
take place at 573degrees C..although it
is, in fact, an ongoing process which may
begin as low as 350C., and may still be
taking place a temperatures as high as
700C

Scumming

Scumming: Unwanted deposits of soluble salts which sometimes appear on the surface of a raw dry pot, or more significantly, on bisc-fired ware. After bisc firing, areas where scum is apparent may be slightly fused and therefore resistant to glaze take-up. Scum is unlikely to resist glaze take-up on a raw pot.

Slipcasting

Slipcasting: A method of making objects by pouring a dense, deflocculated slip into a mould.

Feldspar

feldspar

One of a group of rock-forming minerals, the most abundant group in the Earth´s crust. They are the chief constituents of igneous rock and are present in most metamorphic and sedimentary rocks. All feldspars contain silicon, aluminum, oxygen, linked together to form a framework; spaces within this structure are occupied by sodium, potassium, calcium, or occasionally barium, in various proportions.
Feldspars form white, gray, or pink crystals and rank 6 on the Mohs´ scale of hardness.
The four extreme compositions of are orthoclase, KAlSi3O8; albite, NaAlSi3O8; anorthite, CaAl2Si2O8; and celsian, BaAl2Si2O8. These are grouped into plagioclase feldspars, which range from pure sodium feldspar (albite) through pure calcium feldspar (anorthite) with a negligible potassium content; and alkali feldspars (includingorthoclase and microcline), which have a high potassium content, less sodium, and little calcium.
The type known as moonstone has a pearl-like effect and is used in jewelry. Approximately 4,000 metric tons of feldspar are used in the ceramics industry annually.

Dunting

Dunt: A crack caused by firing and /or
cooling

stress in a pot.

Pyrometric Cones

Pyrometric cones: These are used to
accurately measure the amount of heat
work that has taken place in the kiln.
They are made from precisely measured
combinations of clay and flux materials
which reliably begin to ruse and bend at
a predetermined heat.

What is a Binder?

Binder: A polymetic substance(e.g.
starch-based adhesives) used to
strengthen unfired glaze surfaces

Raku

Raku: A Japanese word which loosely translates as ´enjoyment´, and which strictly only refers to pottery by the potter who holds the Raku title. In the
West, however, the work has become associated with a particular technique which generally involves placing pots into the already hot kiln, and often then carbonising the pots by removing them directly from the hot kiln to a bin of combustible material such as leaves or sawdust.

Suspender

Suspender: A material added to a glaze slop in order to facilitate the suspension of heavy particles in water. Suspenders usually act by the creation of a
macrostructure which hold particles in dispersal.

Pyroplastic

Pyroplastic: The condition of a clay
body in the kiln when heated to
vitrification. At this point, any impact
upon the pot may alter its shape, and,
ultimately, it may begin to sag under its
own weight.

Engobe

Engobe: The word engobe is often used
to refer to decorative (as oppossed to
casting) slips, but may also refer to any
material which is neither a pure clay slip
nor a glaze but which is used to cover
clay.

What is Siccative

Siccative: A drying agent; any material which tends to take up moisture from a slop or body.

Crazing

Crazing: a glaze fault caused by
excessive shrinkage of the glaze in
relationship to the body, and which is
characterised by a network of fine
cracks all over the fired surface.

Flocculent

Flocculent/flocculant: Acids (or salts
which in solution behave as acids) which
alter the electrostatic charges of fine
particles in a suspension, reducing their
mutual repulsion, and thus increase their
forces of attraction. This causes
particles to floc together, increasing
friction and viscosity, thus apparently
thickening the suspension without
removing any water from it.

‘pipe'

A ‘pipe' is the metal rod that runs through the center of lamps through which the cord passes and it is threaded on each end.