it is caused by etching, which I’ll explain in a moment, the improvement may be limited.
4. How to tell whether the cloudiness is residue or permanent etching
This is the first thing I check before I bother treating a whole load of glasses. Put a drop of white vinegar on the cloudy area and wait 1 minute. If the spot clears or looks noticeably better when you rub it with your finger, you are dealing with mineral residue, and the soak will likely help.
If nothing changes at all,
