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What is the effect of heat on some raw materias? |
Unit 1 | Topic 12 | |||||
| Glaze Basics | |||||||
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Many raw materials break down into oxides when heated during the firing process. |
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| In the following example the whiting (CaCO3) molecule breaks down into two oxides when heated to 825 deg. C. The carbon dioxide (CO2) gas bubbles out of the molten glass leaving the flux calcium oxide which lowers the melting point of the glass formers. | |||||||||
|
whiting
(calciumcarbonate) |
heated
to
825 deg.C |
>>>
|
calcium
oxide |
+ |
carbon
dioxide |
||||||||||
|
CaCO3
|
>>>>>>>>>>
|
CaO
|
|
CO2
|
|||||||||||
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Flux
oxide
remains in the glaze. |
Bubbles
out of the
glaze as a gas. |
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|
When whiting
is mixed with other oxides the melting point of the mixture may
be The melting point of a group of oxides together is called the group's eutectic. |
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