I’m traveling through Europe for the first time this holiday season, starting in London. I’m sure I’ll have lots of questions for The Dope, but this is my first: what are the circular distortions in windows around here? I’ve seen a number of windows in which the glass is distorted in such a way that it looks like someone has dropped a rock in a still pond. It is, uniformly, a 4-inch diameter circle with concentric waves terminating in the center. Is this a way to repair glass? Is it an artifact of the manufacturing process for old windows? Why don’t I see this in the US?
See this site for a history of window glass: Period Window Glass. The glass you are describing came originally from the center of the spun plate shown in the diagram at bottom of the page. Obviously it was far cheaper than that cut from the rest of the sheet. Most you see now is probably reproduction glass popular in 70’s along with several other crimes against architecture.
“bullseye” glass may be produced deliberately these days, to reproduce old window glass, and is likely what you saw:
Circular distortions USED to be an artifact of the “crown glass” manufacturing process. See notes in this wiki article: