I did this experiment many times, myself. If you start with boiled water you will get much thinner layer with bubbles. Air actually takes a bit of time to diff

I did this experiment many times, myself. If you start with boiled water you will get much thinner layer with bubbles. Air actually takes a bit of time to diffuse into water if it isn't getting mixed with air (that's why your fish tank needs air to be actively mixed with water). Starting with thin layer of water that was recently hot gives not enough time for any significant amount of air to dissolve. I work with electronics. I use electronic water for parts cleaning. Electronic water is pure water, distilled, deionized, degassed (no oxygen in it) so it does not oxidise copper traces. It does go bad (bad meaning gets oxygen dissolved) when opened, but think more like hours or even days if proper precautions are taken (don't shake or stir once the container is opened).