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Transcript of Kiln Science
Underglaze is matte
Can be made shiny by putting a clear gloss glaze over the top…
Liquid Texture Glaze
What did we learn?
Our Electric Kiln
No new substance is produced
IT IS STILL CLAY!
May involve a change in state
(Think solid, liquid, gas; not Minnesota or Wisconsin)
When it is wet , clay is plastic
As it dries, it becomes a solid
It can usually be reversed
Just add water
To make a permanent change
we need the heat of the kiln to make a chemical change.
New substances are made
Difficult to reverse if at all
May change color
Give off an odor or smell
What happens in the kiln?
What is a kiln?
What does it do?
Bisque Fired: Hard as rock
What is a Kiln?
It is like an oven
The clay is “baked” in the kiln
Kiln “firing” changes the clay!
After Glaze Firing
Is the first firing that clay will go through
Makes the clay insoluble
(It won’t dissolve in water)
Makes the clay porous
(It will absorb some water)
Prepares the clay to accept glaze
times you use a kiln!
Kiln firing causes both
physical and chemical changes
Heat causes expansion
Minerals and elements in the clay change
The structure of Silica molecules rearrange
Gases are released
At 900°F, water (H2O) molecules begin to break free leaving tiny holes* behind
*Remember the tiny holes
At 1100°F the remaining clay particles fuse together forming a glass-like solid.
High Heat + Clay =
burning gases and melting solids
Melted solids+ cool temperatures =
insoluble clay = water will not dissolve it
They are pores that absorb the water in the glaze so the glaze sticks to the pot!
Before Bisque Firing
Just dry clay
Is it a physical change or a chemical change at this point in the clay life?
After Glaze Firing
Glaze: a liquid mixture of minerals and elements that have glass-like properties.
There are 3 glazes we will be using
Answer our Essential Question, How does heat change clay?
The glaze firing is the second time we fire our clay, this time with glaze that we have painted on it.
What would happen if we added water to it right now?
Can it be “UN-DONE” ???
Is it like dough or like a rock?
Physical Change in Clay!!!
Chemical Changes in Clay
What changes do you notice about your clay today?