incompatibility will show up as small cracks or fracture lines where
the two incompatible glasses come together. These cracks will likely
increase with time and may eventually result in a complete
separation. The photo below shows an example of incompatibility.
Click photo to see enlarged photograph.
Photo courtesy of glass artist Deb Compton.
incompatibility, such as that in the above photo, shows up fairly
quickly (sometimes immediately )after firing. More insidious
incompatibility problems arenít obvious to the naked eye and need to
be discovered through compatibility testing.
Although there are several commercially available
compatibility testing products (one of the earliest was called the
stressometer), you can easily make your own compatibility testing
kit. All that's needed is a source of light and some polarized
film. A flashlight will work for the light source, as will a
light table or even a bright window. You can buy polarized
film (sometimes called polarizing film) or you can use two camera
lenses or even a broken pair of sunglasses. Just make certain
that the lenses or sunglasses are polarized, rather than simply
Once you've identified your light source and obtained some
polarized film, you're ready for the compatibility test.
Click here for the next
part of this tip, which discusses how to conduct a
Copyright 2007 Brad Walker.
All rights reserved.