You have heard it before, “Don’t believe everything you read!” I know this, but never expected it to apply to what I read in my glass fusing books.
All of the books I own stress how important it is to have the glass clean before fusing it to prevent devitrification. At least one of the books I own suggests using vinegar to clean the glass. I use alcohol occasionally but mostly I use vinegar because it is less harsh. It seemed to work fine, but the other day I discovered a problem with using vinegar. From now on I will be using alcohol.
After full fusing a set of plates, I was getting them ready to slump and cleaned them with vinegar. As I wiped the plates dry I noticed a haze and some spotting that wasn’t there when I took the plates out of the kiln. I think it was a mild etching from the vinegar. I noticed this kind of haze a few other times, but didn’t realize until just then that it was the vinegar that caused it. Nothing I tried to clean it with removed the haze. The only thing that worked was a bit of hand polishing with cerium oxide.
It was difficult to capture the haze in a photograph. In the photo below, if you look at the reflection of the overhead light you can see the haze on the bottom half. The top half is where I polished it out.
Always something new to learn!