This is part two of a two part series on
striking. Click here to go to the beginning of the series.
Striking, the process in which the color or transparency of a
particular glass changes after being fired in the kiln, can't
usually be prevented. However, undesirable color changes can
sometimes be made less likely by careful firing.
One way to
try to do this is to minimize the time spent in the temperature
range where the glass colorants precipitate. Done
successfully, the color change may not be as dramatic; in some cases
it can be avoided altogether. Unfortunately, it's very
difficult to fuse without spending enough time in the temperature
range for the color to change, but firing speed and time spent in
the temperature range can impact the degree of color change.
In addition, different lots of glass can vary in color after
firing. This is because the manufacturing process isn't necessarily
stable over time. Changes in processes, changes in formulas from
batch to batch, and (oops) even mistakes, can all impact the
characteristics of the glass.
Striking issues are most likely in colors like the reds and
the more unusual glasses. More unusual usually means that it's more
difficult to make and that the manufacturer has less experience with
Also, using an overspray (such as Spray A, SuperSpray, or a
borax solution) can change the striking process. Since an overspray
is just particles on top of your glass, using it just makes a
complicated situation even more complicated.
Copyright 2005 Brad Walker.
All rights reserved.