I have been cleaning windows for quite a while now and have run into some deposits on windows that do not respond to acid cleaning like water stains or mineral deposits will. These stains normally appear on older glass and are reddish with a kind of rainbow haze. I have tried the acid wash, razoring vigorously, and fine steel wool. Any other suggestions?
From the description, I am baffled. I feel certain I could help if you provide a phot. Until then, check to see if any sprinklers are near by....the "rainbow" haze you speak of indicates iron oxide...easily removed with the right acid.
Also, are these commercial or residential windows?
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