|Monthly Tech-Tip |
ASTM C24 -01
Pyrometric Cone Equivalent is measured by making a cone of the material and firing it until it bends to 3 oclock.
The cones are the size of small orton kiln-sitter cones and they are set into special refractory rings that hold them at the correct angle to bend inwards. A ring can hold many cones so many tests can be done in one firing. The ring is fired in a small kiln capable of cone 25-30 (clays that normally mature at cone 10, for example, might not melt until cone 20 or higher). When placing the ring into the kiln the placement of the cones is noted (to identify them) and the temperature at which each bends is recorded.
These bars were fired at cone 10, they were straight when dry. The back one is a cone 10 Grolleg body, the front one is a cone 6 Grolleg body. This simple test is valuable to determine susceptibility to warping in porcelains. If the pyro-plastic deformation is too much, for example, the weight of a handle will pull the round rim of a mug into an oval shape, for example.
Simple Physical Testing of Clays
Learn to test your clay bodies and clay materials and record the results in an organized way, understanding the purpose of each test and how to relate its results to changes that need to be made in process, recipe and materials.
Frit Softening Point
In ceramics, this is the temperature at which a glaze or glass begins to flow, ceasing to exhibit the properties of a solid.
Frit Melting Range (C)
In the ceramics industry, clays that are resistant to deforming and melting at high temperatures are called fireclays. Kiln bricks are often made from fireclay.
Test conducted primarily on materials use to make bodies or glazes.
|By Tony Hansen|
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