I’m certain that I’ve done this one before but can’t find it. I talked about having lead above glass.

See this picture : -

https://www.dropbox.com/scl/fi/15k1oufc1bdnmtthlvbe8/lesson-to-learn.heic?rlkey=sgq0970dw33medi6mk29ceupv&st=vyoi58g9&dl=0

The white streaks running down the Glass are caused by rainwater slightly dissolving the lead, which you can just see above the glass, and taking tiny amounts of lead oxide down the glass. You might think that you could just clean this off easily. You can’t. The lead oxide etches the surface of the glass irreversibly. Ugly and fully preventable.

All architects, glaziers, conservatory manufacturers and in general anyone who specifies glass for use on roofs needs to understand this. And never use lead above glass.