Kat in the Hat on wed 15 may 02
The ratio of silica to alumina is mainly responsible for the
degree of matteness in glazes. In the absence of boron,
ratios of less than 5:1 are generally quite matte; ratios of
greater than 8:1 are usually glossy in the absence of high
titania, zinc, magnesia or calcia (which cause volatile
melting or crystallization during freezing). Ratios of 18:1
are possible, but certainly not typical. If a glaze remains
matte when fired higher, it is a true alumina matte.
kat@digitalfire.com
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