What is it?

Took me a long while to work out what this photo was!
Quite often I take a photo accidentally when I am putting my phone away after taking a shot and knew that this was one of those incidents however trying to work out where and what of had me puzzled but I liked the effect of the slight swirl!
Worked it out in the end! I had been taking a photo of the cool patterns emerging as I mixed PVA with water for an art project at school and must of hit the shutter release as I sat my phone up on the self out of harms way. The tile are the roof tiles!