Bottled Bubbles

Washed out a bottle of oil (use by date 2007) and noticed after a quick rinse with detergent prior to recycling that it had quite nice bubbles in it. Decided to have a try at a photo and this is the result. The bottle was roughly square with flattish sides and this is just a small part. Most of the bubbles were quite large and rough cubes but I liked this bit showing a cluster of smaller bubbles and the complicated way they arrange themselves. Possibly into a low-energy configuration. Back-blipped when I realised I'd nothing better for today.
Added to say the bubbles were more or less colourless and little contrast but got the intersections to show by playing with the curves menu.