An "inclusion" is a material that is trapped within the layers
of glass when it fuses. Inclusions can give a piece texture,
character, and color that glass alone can't achieve.
The key criterion when using inclusions is that the foreign
material, which may have different expansion characteristics than
the glass, is thin and weak enough to allow the glass to expand and
contract normally. If it is too thick or strong, or has a
dramatically different COE, it will cause the glass to crack as it
Aside from air bubbles, which are present in most fused
pieces, the most frequently used inclusion is probably copper.
Other common inclusions include gold and silver foil, but organic
materials (such as leaves and various fruits and vegetables) can
also be used. Experimentation often pays off with unexpected
results -- just be sure to use items that are small or thin enough
that they can be contained within the glass without cracking.
For a list of inclusions by
category, click here.
Copyright 2005 Brad Walker.
All rights reserved.