Frosted Security Glass Can Be Defeated With What Common Item?
Answer: Cellophane Tape
Frosting glass by etching the surface with an acidic compound or sandblasting it is a common way to permanently increase the privacy and security offered by the glass.
It would appear to be a completely irreversible process short of painstakingly polishing the glass until the etched layer had been completely removed, but there’s a neat little trick that allows you to look through security glass that is only etched on one side: you can press a piece of cellophane tape over it.
This bit of office-supply wizardry works because the cellophane tape temporarily fills in the irregularities of the etched surface (you could approximate the same effect, albeit in a much messier fashion, by smearing oil over the glass). The result isn’t as perfectly clear as regular sheet of glass but you can still easily look through it and identify what is on the other side.
Image captured from a video by TheFarmacyMan.