Thanks to some posts on a previous thread by me, comparing Crystal Clear to MDR, I've been reading up a bit on acid cleaners such as Winsol Crystal Clear 550, which uses 3% Hydrochloric acid, and 3% Hydrofluoric acid, which is utterly nasty stuff, can seep into your bones, destroy any type of tissue etc. Using proper protective equipment such as gloves and goggles is should be allright. I'm not sure how dangerous Crystal Clear is at those levels of acid content, but if you read into those acids on wikipedia or anything it's quite scary.
What I can't figure out is if all double glazing units are still made out of float glass, if so it's melted on a layer of tin. Use Crystal Clear 550 or any acid cleaner, and it instantly smokes/hazes the glass. Appararently only one side has got a small amount of tin in it and can be spotted with UV light or digital tin detector. Is glass still manufactured this way?
"Hydrochloric and hydrofluoric acids. Make sure you wear gloves with any type of harsher acid. Warning this will smoke/cook float glass. The chemicals in this product react with the tin in the glass. You can detect the tin/air side of the glass with a UV light or with a digital tin detector. CC550 will work safely on the air side of the glass. It is recommended to test the product on a small area of the glass to make sure you will not "cook" it before applying this product to the entire window. You want to work relatively quickly with this product if you are in hot areas."
I must say it's ridiculously quick and easy to remove even heavy staining of glass using Winsol 550, but I think I will stick to something like Viakal unless I absolutely have to.
http://www.liv.ac.uk/safety/Hazard_A_to_Z/Hydrofluoric_Acid.htm