|Monthly Tech-Tip |
It is not nearly as important to know the chemistry of materials for use in clay bodies as it is to know about their physical properties. Anyone can evaluate a clay material and produce a report that can be very helpful to others. This can be done by examining it and answering some simple questions.
Does it contain lignite or decayed plant matter, does it smell bad?
Does it shrink alot on drying?
Does it fire to cone 10 or 6 without melting?
How much does it shrink when fired and what is it porosity at various temperatures?
Is it plastic enough to wheel throw on its own?
Does it make a nice slurry or does it gel? Does it stay in suspension well?
Will it deflocculate?
Does a normal glaze craze or shiver on it when it is fired to cone 6 or 10?
How fine is it, how much residue is left of a 50 mesh screen? 200 mesh?
Does it contain much soluble calcium (does it fizz when acid contacts it)?
Does it have soluble salts that produce a colored scum on the fired surface?
Answers to these kinds of questions would tell people alot about the material.
Test conducted primarily on materials use to make bodies or glazes.