1. 5 stages in the firing cycle
Water smoking- occurs when the temperature in the kiln reaches 212˚F, all remaining surface water is burned off, enough steam is often generated to be seen. Hence the term water smoking. Water boils and turns to steam at 212˚F. If the steam leaves the clay too fast, the pot explodes just like if you boil eggs too fast, they crack.

2. 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.
Quartz Inversion °F. The quartz crystals in the clay undergo a change called the quartz inversion. The crystals grow and change in shape.
Oxidation - the burning off of organic materials occurs at 1600°F to 1700°F. This has no chemical effect on the clay, but it does leave the clay more porous.
Vitrification - Partial vitrification begins as the temperature rises. This will be determined by the type of clay body. Clay with a high alumina content (stoneware and porcelain) will vitrify more slowly and at a higher temperature than clay high in fluxes such as iron or talc (earthenware). Vitrification, you will remember, is melting of the clay platelets. Complete vitrification results in a glasslike material; therefore, clay ware is never completely vitrified.

3. Glazing and Finishing
Glaze- glass like coating put on pottery to make it waterproof, melts when fired, hardens as it cools
Glaze application techniques:
Dipping

4. 2. Spraying
3. Pouring/dripping

5. Brushing/painting

6. …a little art history The Chinese discovered
wood ash floating through the
kiln and when it landed on the
pottery it created a shiny
surface (but isn’t considered
real gaze)
The Egyptians were the first
to use true glazes since about
5000BC. They dug their clay
from the Nile river and used
sand from the desert to make
glaze.

7. Ingredients of glaze
Glass former – (silica or sand) creates the glossy surface,  silica forms glass all by itself. However, silica melts at about 3100⁰ F, which is much too hot for ceramic kilns. As such, it cannot be used on its own.
Flux – aids melting, keeps surface of pottery from oxidizing so the glaze can attach, lowers the melting point of the silica.
Refractory (alumina) – resists melting, aids in high temperature firing, stiffening agent.

8. Glazing Tips Keep a “dry foot”. (no glaze on the bottom) Why???
Use a pencil (regular #2,
not a mechanical) to draw a
thick line around the bottom
of the glaze edge. Why??
Glaze “takes” best on the first
firing. Why??
Dip glazes once, (unless it’s thin
enough, or you are crossing colors).
Why??
Brush 2 or 3 layers. Apply coats as
soon as the sheen of the coat before is
disappearing. Why??

9. ..Other ways to finish your piece
Burnish- “to polish by
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
spoon.
Sgraffito- a colored slip
is applied and often burnished
to the pottery surface then a
design is etched or carved out
of the applied slip.

10. …other ways to finish your piece cont...
underglaze
Photo transfer
Slip trailing
Glaze transfers