Many
people take their fusing glasses beyond the tested parameters of the
manufacturers in pot and screen melts and combing and casting
operations. It has been speculated that there are compatibility
shifts of hot colours and of opalescents.
Reading,
and some experience, lead me to the belief that is the colouring
minerals that are the key to which glass will shift in compatibility.
Colours made with sulphur and selenium are more likely to opalise
and also change their compatibility at extended times at high
temperatures. Extended time is in the region of an hour or more.
High temperatures are those over 850ÂșC
The
colours at most risk of compatibility shift seem to be:
Reds
Oranges
Browns
Ambers
and a
few bright and olive greens, but not dark greens.
Of
course testing, using polarising light filters, is required to determine which will remain compatible after long,
high temperature firings. A method of testing is given here.
High temperature compatibility shifts are discussed here.
High temperature compatibility shifts are discussed here.
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