HF acid can damage car

Q: I had my Honda Accord detailed, and when it was returned, I noticed significant water spots on my rear-view mirrors and the outside of the back window. I can only assume they were using hard water and did not wipe the windows fast enough. Although I'd like to hold them responsible, proving it was their fault is difficult. I have tried to remove the spots using a slightly diluted white vinegar solution, and also with a baking soda/vinegar mixture, with zero results. Is there any product to remedy this? Any suggestions, short of replacing the glass and mirrors?

— L.Q., Batavia, Ill.

A: We have a hunch the problem may have been caused by hydrofluoric acid (HF). It etches glass. Hydrofluoric acid is used in many automatic carwashes because it does an excellent job of removing brake dust, road grime and rust — and it is inexpensive. Diluted properly, it leaves cars sparking clean, but higher concentrations etch glass. We know of no way to remedy this. You may be able to feel the etching with your fingernail. The professional carwash industry generally decries HF, but some operators still insist on using it, especially to clean wheels. HF is insidiously dangerous, since it doesn't cause skin burns that you can feel as other acids do. Instead, it seeps through tissue, eats into bones and turns the calcium into calcium fluoride. It may take hours before the burn victim realizes it.

presume "detailed" means washed and serviced. I wonder if they use HF here?