i posted this on a honda forum(my prelude):
same thing happened to me and ive spent the last year trying different things. The only thing that ended up working was a solution called "bio-clean water stain remover". I picked it up at a local commercial solution store for $15. Took it home and got to work.
here is a before pic, and it really doesnt do it justice for how bad it was:
i did the drivers window in about 10 minutes but dont get me wrong, its alot of work.
Dont be mistaken, the first picture is of my window, what your seeing is the reflection:
same with the 2nd:
you can also find this product online. Search around though some are priced at $21 and others at $13 so price shop because they are all the same product.
It is safe also if it gets on your molding, i got some on my molding and you just wipe it off. Its only harsh when you buff it into something. Its really just like a compound with a few chemicals. And for anyone who knows these water spots im talking about, they know that 2:1 solution of water with vinegar, a razor blade, Wheel polisher, scrubbing bubbles, Simple green, Oxi Clean, magic eraser, C L R, Coca-Cola, Rain-X, or Brillo pads, None of these work. None of them are designed to work for this purpose.
Spots caused by hard water, acid rain and other staining agents have always been a problem on automobile glass. Most detailers try plain glass cleaner and go no further. Others sometimes try methods that may damage the glass itself. But there are safe ways to remove most spots.
Ill try and get a little more in depth of hard water while keeping it simple. Elements such as calcium, magnesium or iron give water undesirable characteristics we call "hardness" that cause spotting on glass (and paint). Calcium ions are formed by a reaction of calcium carbonate (limestone) and carbon dioxide in wastewater. Hard water, also sometimes called acid rain, is only part of the problem. There is also a chemical reaction between these minerals and commercial fertilizers which can leave a cement-like deposit on glass. Acid rain, a result of environmental pollution, when mixed with water creates an acid that can spot or even etch glass. A MAJOR cause of hard water is if you have a well.
Commercial window cleaners use acid-based cleansers similar to those detailers use to clean wheels. The acids can be a quick and easy way to remove many stains and spots from windows, but they do require understanding and caution in their use. There are two types of acids: organic and inorganic. The inorganic group includes hydrochloric (HCI) and hydrofluoric (HF, also called muriatic) acids. Organic acids are active or "critic" and are derived from fruit. They are used in colas. (Makes you want to put that Coke away, doesn't it?) An inorganic acid can lift, suspend and dissolve water spots.
Here is a direct
LINK to my thread in the Honda Forum.