Expert: Robert Lamb - 8/16/2011

Question
Hi,
We had a mason stripping paint from marble and brownstone on our condo building in Boston's Back Bay. Let it suffice that the whole experience was a disaster, we now have a new mason hopefully completing the job correctly.
The original guy did not protect our windows and they are now "etched" with cloudy "droplets" which we have not been able to remove with window cleaning. Someone suggested trying Zud.
What would you suggest?
Thank you so much!

Answer
Aline,

There are basically two things you can do if the glass is etched. The first option is to use mechanical action, basically buffing out the etching. 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 chemical etching 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. After glass restoration with this chemicla processes, the glass needs to be cleaned using standard proceedures.

If you opt for the mechanical method of removal, that too includes the use of compounds (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.

Please let me know how things turn out.

Sincerely,

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