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updated thu 10 aug 06


Tom Buck on tue 8 aug 06

The term specific gravity was invented by a chemist (long ago) to
symbolize the density of materials, in our case "liquids" (solutions,
slurries, dispersions) as referred to the density of water... that is, if
a cup of water weighed 200 grams (not including the ceramic cup itself),
and a cup of glaze liquid (slurry) weighed 306 grams, then the specific
gravity of the slurry would be 306/200 = 1.53.
but today, chemists prefer the term density (without special
reference to water) in grams per milliliter. so if you "tared" the cup
first, then weighed it full of slurry (200 milliliters of slurry), and the
weight of the slurry was 306 grams, then the density would be 306/200 or
1.53 grams per milliliter. the water reference is not needed because 1
milliliter of water weighs 1 gram, so dividing by "1" does not alter the
density value.
as for glaze slurry densities: if you spray, a good range would be
1.42-1.45 g/mL; if you dip, then 1.53-1.55 g/mL would give serviceable
results; and if you brush, then make the slurry denser, to 1.62-1.65 g/mL.

good pots peace Tom B.

Tom Buck ) -- primary address.
"alias" or secondary address.
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
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