Ivor and Olive Lewis on sun 25 jun 06
Dear Ben Shelton,
Powers of recall seem to diminish with age.
I forgot to mention that crystal precipitation leading to opacity and =
translucency in glazes can be encourage by slow cooling. This involves =
having ingredients in your glazes that will dissolve and decompose then =
recombine with other elements to create new minerals. Most of these are =
transparent and colourless but are evenly distributed as microscopic =
fragments throughout a silicate glass matrix. Again, they have differing =
refractive indices which causes reflection and refraction of incident =
light.
Principle ingredients to maintain whiteness would be Calcium and =
Magnesium compounds. Other compounds to promote this effect would be =
those which contain the elements Strontium, Barium and Zinc. Glaze =
thickness can have a great influence on the development of optical =
effects.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
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