Stressometer, excl. batteries, excl. 2nd polaroid sheet

Operation stressometer:

1. On the light source is a polaroid, the polaroid sends the light in 1 direction.
2. Above this you place/hold a 2nd polaroid.
3. Turn the polaroid until you no longer see any light.
4. Now hold the glass you want to test between the polaroids.

If there is stress / tension in the glass, this is where the light is turned, you will see the stress light up white.
You can only use the stressometer on transparant glass.

Batteries are not included, there are 2 options for this: 4x R20C or 1x 4R25C

The 2nd polaroid is not included, you must order it separately.