Expert: Robert Lamb - 1/14/2012

Question
Hi Robert
I hope you can help me with this tricky window stain and if not, perhaps you could point me to someone who may have expertise in this particular area. About a year ago I came across the marks on a glass window that I hope you can see in the attached pictures. It's almost like someone has flicked a quantity of milky liquid onto the window. I have tried every possible cleaning agent I can think of on it and even steel wool and nothing will budge it even a bit. This year as I was doing the windows, I notice that I am getting it on more windows along the same side of the house but to a lesser extent. It's very frustrating as I am usually pretty good at cleaning. Any ideas?
Barb

Answer
Barb,

Yes, that's a tricky one. Thank you for the photo. If you have any other photos of this, it might help. You can send any you have to my email address robswindowcleaning@yahoo.com.

I have a few ideas about this. But first, you really need to find the source of this problem. Do you have any water sprinklers that are spraying your windows, maybe even an automatic sprinkler system? If you do, then that is the source of your problem. It looks like to me what you have here is what is commonly known as "hard water spots". My best guess with the information given me is that water is hitting your windows (and probably the siding on your house) and as that water drys the minerals in the water are drying on the glass leaving that stain. Depending on where you live you can have either "hard" or "soft" water. What that means is your water has a lot of dissolved minerals in it or is could almost be mineral free. The more minerals it has, the more likely your glass will be damaged if you allow tap water to dry on the glass surface. Another possibility, related to this is that water sprayed on your house siding is leaching any minerals from the siding of the house and re-depositing them on your glass. This would especially be true if you have stucco or brick siding on your home. The worst kind of mineral deposit for glass is silicate deposit which is so closely related to the makeup of your glass that it forms a very hard bond and can be difficult to remove. But it can be removed.

If my assumption is correct, you have basically two options to remove this stain. The first option is to use mechanical action, basically buffing out the built up mineral deposits. The second is to use chemical action, let the chemical remove a fine layer of glass to reveal a new, smooth layer.

We have had a lot of success removing hard water spots using a product called Crystal Clear 550. The product is an acid based formula that includes hydrofluoric acid. The product must first be tested in an out of the way area. If it is going to work, it will work like magic. It's as simple as wiping it on and wiping it off. In rare cases it will cause an acid burn that will make the glass have a tin haze or greyish spot. Without getting too technical, tin haze has to do with the way float glass is made. The important thing when using this product is to test it as mentioned above and closely follow the safety directions on the bottle.

If you opt for the mechanical method of removal, that too includes the use of chemical compounds that will remove a fine layer of glass revealing a polished, smooth glass. Zud is a cleaning product that may work, but it is at the very low end of the scale as far as effectiveness is concerned. It is also very labor intensive. If you decide to use the mechanical method of stain removal, there are other products that would probably give you much better results.

Actually you can find all the supplies mentioned above online at a window cleaning supply house like ABC Window Cleaning Supply or J. Racenstein, as well as others.

Here's the chemical method link to one supply house: http://tinyurl.com/2br7hcy

Here's a link for tools you will need if you choose the mechanical removal option: http://tinyurl.com/38kbx7s. Again, if you go this route, you will also need some of the chemicals in the link above.

Of course, if you don't want to tackle this project yourself, you should look for a window cleaning company that specializes in glass restoration. If you need one, give me a shout as I know literally thousands of window cleaners around the world.

One other thing I should say is you should really put some sort of protective coating on your glass once it has been restored. A low tech product would be something like Rain-X and a high tech product would be something that uses nanotechnology. I can help you with that too.

Please let me know how things turn out.

Sincerely,

Robert Lamb
Window Masters
http://www.window-masters.com