A polariscope is a tool to visually detect stress distribution in transparent material, using polarized light.
It is used by glass blowers to check if their products are safe and meet the quality standards. As Raymond, a chemical glass-blower from Forest Gate, stated, “Strain is like a ticking bomb, it can crack and break a glass piece anytime and you cannot know when it will happen”. Material stress is a crucial part of a glass blower's practice, and it occurs when heat is applied to glass.
Unlike a common wall-mounted strain viewer, this polariscope doesn’t require electricity and can so directly be employed by the worker at his workspace, whether it is at his bench or at the lathe. It is small in size, robust, cheap and portable.
Strain is visualised by putting a glass piece in the gap of the tube, and by looking through the piece and the filter, strain, if present, manifests in colors ranging from blue, green, red to yellow.
The insights and feedback of craftsmen and designers were crucial for the development of this project, particularly of Dr Matthew Foreman (Imperial College), Jochen Holz and Steve Ramsey (glass blowers), Chem Glassware Manufacturers, Dixon Glass and Max Frommeld (designer).