Rainbows come in Threes

My friend messaged me today with an request to take my camera with polariser into work tomorrow. He wants to demonstrate how an iPad and camera with polariser can be used to create photoelastic or cross polarised pictures of plastic objects to our camera group, and couldn't find his poloariser!

I sorted mine out, but thought I'd have another go myself, just to check it still works!  When I tried this a couple of weeks ago I managed to get a black or white background (depending on the angle of the polariser), but I was using a larger computer monitor screen.  The iPad didn't seem to give as strong a result, but it demonstrates the effect and is colourful never the less.  For a little more interest I worked two of the shots up into a triptych