Polarized film sheets for testing fused glass for internal stress. Two very high quality sheets of polarized film. We buy this directly from the manufacturer, it’s made in the USA. Available in 4 sizes for any sized studio:
6″ x 6″ $15
8″ x 8″ $25
12″ x 12″ $48
17″ x 17″ $68
Each is a SET OF TWO sheets, each mounted in sturdy black poster frames. Size listed is the film size, the frame is larger.
Polarized film has microscopic lines that channel the light. When one sheet is turned at an angle, direct light is blocked and refracted light is detected. Internal stress in the glass will cause a visible flare. Internal stress can be caused by tempering, poor annealing and incompatibility. This film will not prove compatibility, other tests are required to confirm.
For articles regarding testing glass with polarized film, please visit:
For detailed instructions about how to test bottle glass for compatibility, and fusing mixed bottle glass safely, the on demand Advanced Bottle Glass Fusing class covers that topic, among many others. To learn more about Jodi’s online classes, visit the Online Class Page.