Hotline Polaroid Filter Set

Hotline Polaroid Filter Set - Stress Tester

Used to assure compatible glasses. Use: To observe stress, place the fused glass test strip over the polariod filter. Hold the second filter closely over the fused strip sandwiching the glass between the filters. Rotate the filter until the maxium light blockage occurs. At this point a halo or flare will appear if excess stress is present. The halo will not appear if stress does not exist. For best results use with a light source.