Photoelasticity - Making Rainbows :)

This weekend's lockdown project was a little one, but it was really interesting. I explored Photoelasticity! It's the way that the "stress" in plastic looks when seen through a polarising filter, and against polarised light such as an LED screen.

I tried it with a variety of objects, but a plastic wine glass was the best.

I put a white background on my PC, and put the cups on a piece of black card in front of it.

Not very interesting, right? Although, even without the polarising filter we can see slight rainbows on the edges of the cups!

So I put my filter on, gave it a twist... and magic! The white background when black, and rainbows appeared all through the cups.

Amazing!

I also found that a pen lid, a tippex mouse, and a fruit pot tray gave great results too. Water bottles and Coke bottles, not so much.

Finally, I put a cup back in front of my tablet rather than my PC screen, and instead of darkening the backdrop, the polariser made more rainbows!

It was good fun to have a go at this. If anyone else has a polarising filter, I recommend giving it a go and seeing what you come up with!