© Paul TarlowAll rights reserved.
Anything embedded in glass (intentionally or not). Common inclusions metal foils and air bubbles.
The material being included must have the same expansion rate or be of sufficiently little mass (or softness) that it does not cause excessive stress within the glass.
When the metal tools used to stir batch corode and result in accidental inclusions it is called scale.
Since Janauary 1, 2005 there have been HUNDREDS OF THOUSANDS visits to this site.