THE 7 STAGES OF
CLAY
STAGE 1: RAW CLAY
This is clay in its raw, natural
state when dug up from the
ground.
The color and working properties
depend on the location where it
is found and the minerals and
impurities present in the clay.
STAGE 2: SLIP
Clay that is in semi-liquid form
is called Slip. It can be poured
into molds or used as glue to
bind two pieces of moist clay
together.
STAGE 3: WET CLAY
(PREPARED)
Prepared clay (wet clay) has
been processed to remove
most air bubbles and impurities.
Various additives have been
included to make it more
malleable, fire more evenly, etc.
Wet clay is also known as
Plastic clay because this is the
stage where it is easiest to
Work.
STAGE 4: LEATHER HARD
When clay has dried to a point
where it holds its form but
maintains a degree of moisture
so that it feels and works like a
piece of leather it is called
leather hard. Although it's still
semi moist it is strong enough
to support itself and keep its
shape when pressure is applied.
This is the stage where designs
can be carved or a handle added.
STAGE 5: GREENWARE (BONE
DRY)
Greenware is when clay is
completely air dried, and since
Greenware is basically dried mud
any contact with water will return it
to its wet or slip stage. This stage is
also when a clay piece is in its most
fragile state; a tiny nudge could easily
damage the piece. Clay must pass
through this drying stage before it can
be put in the kiln for its initial bisque
firing. Any excess moisture left in a
piece will expand into steam in the
kiln and destroy the work.
STAGE 6: BISQUE FIRE
Bisque clay is clay that has
undergone a first firing in a kiln.
After about 660 degrees the heat
begins to evaporate the last
molecules of water. When the kiln
temperature reaches the maturing
point of the clay (c. 1888 degrees
for earthenware) it transforms it
into ceramic material. At this stage
it can no longer be affected by
water nor changed in any way.
However, it is still porous and will
not hold water for very long.
Bisque is the preparatory stage
for glazing.
STAGE 7: GLAZE FIRE
Once your piece has been
Bisque fired it needs to be
glazed and fired again to
enable it to hold liquids. Unlike
paint, glazes cannot be mixed
to create secondary colors.
Glazes are chemical/mineral
formulae that mature at a
specific temperature to create
a glassy coating in the desired
color. Mixing them corrupts the
formula and creates
unpredictable results.