Intro to Ceramics/Clay. Clay Makes up 75% of the earth’s land mass!!. 3 Properties that make up clay. 1. Plasticity (ability to form). 2. Porosity (ability to hold moisture). *Similar to a sponge. 3. Vitrify (ability to harden and keep its shape). 3 types of clay.
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1. Plasticity (ability to form)
*Similar to a sponge
Clay is characterized by it’s iron content (color), vitrification process, and firing temperature.
-low fire temperature (1800 degrees), red in color, often used to make Mexican pottery and flowerpots.
-medium fire temperature (up to 2200-2300 degrees), tan or buff in color, often used to make everyday dished, mugs, etc.
-high fire temperature, white in color, often used to make dolls, China dished, toilets, sinks
-removes the air bubbles
-prepares and aligns the platelets in the clay
-develops a uniform texture
-----When building objects with clay, it is important not to trap air inside the clay. This will cause the piece to explode in the kiln.
Score- lightly put in hatch marks
on both pieces to be attached
Slip- (liquid clay) add this muddy
substance to both of pieces of
clay you are attaching
Weld- put the two pieces together
and blend, it is sometimes necessary
to add an additional coil to the seam
to make it stronger
- Any clay that has not been fired in the kiln is considered greenware
3 stages of greenware
Workable- clay is very moist and pliable
somewhat moist and easily
be carved but breaks easily
Bone dry-clay is lighter in
color and warm to the touch
--Your clay piece can crack or warp when it dries.
Loop, Carving, trimming Wire cutter
Kiln- oven like machine that “fires” (bakes) the pottery
Bisque Firing- 1st firing,
about 1750-1800 degrees.
When it comes out of the kiln
it is called bisqueware
Glaze Firing- 2nd firing,
anywhere from 1800-2300 degrees.
When it comes out it is called
--It takes about 2 days to go through a full firing cycle.
--Clay looses it’s plasticity after it has been fired, and can NOT be (recycled) or reused at this point.
Dehydration-660˚F, the chemical water, starts to burn off, by 950˚F the clay is completely dehydrated. It is now a chemically different material than it was when put into the kiln. Now it is aluminum silicate known as mullite. The change is non reversible.
Glaze-glass like coating put on pottery to make it waterproof, melts when fired, hardens as it cools
Glaze application techniques:
wood ash floating through the
kiln and when it landed on the
pottery it created a shiny
surface (but isn’t considered
to use true glazes since about
5000BC. They dug their clay
from the Nile river and used
sand from the desert to make
on the bottom) Why???
not a mechanical) to draw a
thick line around the bottom
of the glaze edge. Why??
enough, or you are crossing colors).
soon as the sheen of the coat before is
rubbing to a high sheen” Often
with pottery, a slip is applied to
the surface of the clay when it is
in the late leather-hard stage then
polished with a smooth rock or
is applied and often burnished
to the pottery surface then a
design is etched or carved out
of the applied slip.