Thanks to my team mates for all the supportive comments and suggestions!
These are two ordinary rulers. The technique I used is called Cross Polarization, and involves putting a transparant plastic subject (or two) between a polarized lightsource (my screen) and a polarization filter, that is set to cancel the already polarized light out. It then shows the stress patterns within the product in pretty colors. Loads of fun. Now can I choose the next theme?:)
Like Albert Einstein, I now know 99 ways not to shoot this picture. ;)