Stress Lines

Forecast was for a very miserable day so I was out early to shoot the sunrise. Unfortunately the sunrise was fairly insipid and I returned home resigned to another bad weather shoot later. However I remembered a technique I wanted to try indoors and today seemed the right time to have a go.
The approach is very simple, an LED light source - in this case the Flashlight app on my iPad - some transparent plastic cutlery and a polariser on the lens. The result shows the stress lines in the plastic as bands of colour, rather like the lines of colour you can see in a car windscreen when you wear polarised sunglasses.
Easy to do and no need to get wet doing it.