Joseph Herbert on sun 9 may 10
DJBrewer88 wrote: "I have Stephen Murfitt's Glaze Book and have found some
terminology differences. One ingredient called for in some recipes is
quartz. Is this the same as flint or silica?"
All these names. Silica, Flint, Quartz...All SiO2. Also amethyst,
Citrine, Chalcedony, jasper, and agate. All SiO2.
There is a legacy of "common" names in ceramics that were once the norm, bu=
t
now have more chance of causing confusion than giving clear direction. It
seems there was a recent confluence of volcanic ash, soda ash, and pearl
ash. None are really "ash" in the sense of the remains of something burned=
.
Volcanic Ash is very fine rock particles, soda ash is sodium carbonate
(Na2CO3), and pearl ash is potassium carbonate (K2CO3). Of course, bone
ash really is burned bones, so go figure.
The "ia" ending kind of means oxide of, as in silica, titania, and alumina.
All are oxides of the indicated materials, silicon, titanium, and aluminum
(or a character in "Mid-summer's night dream"). Boria is a rare usage but
would be the oxide of boron. Of course, it is not always so: Lead oxide is
litharge, Iron oxide is rust (not Ferria).
It is better and less confusing to use the chemical symbols, or to at least
reference them when referring to a material, rather than just assume
everyone knows. The usages for the various ceramic materials varies fairl=
y
widely among the English speaking potters, depending on their country of
origin. Throw in a few 50 year old books, things get interesting. The 194=
6
Lange's Handbook of Chemistry has a very interesting ceramics section.
Joe
Joseph Herbert
Training Developer
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