Striking is a process in which the color or transparency of a
particular glass changes after being fired in the kiln. In some
cases this is desirable, but in many cases the effect is not wanted.
Red glass (especially glasses with cadmium red) tends to strike more
often than other glasses.
Striking is related to the manufacturing process and to how
the colorants in the glass precipitate in the glass as it cools.
The process goes something like this:
1. The manufacturer rolls out the glass into sheets.
2. The sheets cool, with the coloring substance precipitating
in the glass as it cools. This gives the glass its original color.
3. Because the sheets of rolled glass cool very fast, some of
the coloring material is trapped in the glass -- it doesn't
precipitate as a visible color, it's just there.
4. Later, when you reheat the glass in your kiln, there is a
temperature at which the color will precipitate again, changing the
color (and the color density) in the glass. This range appears to
differ for different glasses, but is somewhere from around
1150F/620C to fusing temperature.
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Copyright 2005 Brad Walker.
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