Bubble wrap
When I first got my new phone I daren't take it anywhere in case I damaged it. That sort of defeated the whole point of having it so I bought a plastic case and screen guard. I was in such a hurry to protect my new phone that i put the first screen guard on the wrong way round which didn't work to well since a, it didn't adhere to the screen and b, it was sticky. Second time was better but got a lot of small bubbles trapped between the guard and screen. The photo shows attempt 3. Difficult to take the photo since my phone is my camera however I made do with my web cam. It's interesting how the bubbles have different sizes. I wonder if this is due to the different size particles of dirt that must be stuck to the screen. Could be an interesting investigation although measuring the size of these tiny particles could be challenging.