Expert: Robert Lamb - 11/18/2010

Question
QUESTION: I recently built a new house with stone exterior walls. After heavy rain a white scum forms on the windows that looks as though it has come from the walls. This dries into a white powder. How do I clean this off?

ANSWER: Brian,

The white powdery scum you're seeing on the outside of your new house is efflorescence. Efflorescence is composed of salts and other mineral-like material that remain in almost all masonry products after manufacture. Are you asking how to remove efflorescence from your windows or from the side of your house?

If the stain you are trying to remove is on the windows, you might be able to just clean the windows with a squeegee and water with a few drops of dish washing detergent in it. But if this has been going on for some time, the minerals from your masonry products are going to attach themselves to the glass, which after all, is made of similar minerals.

There are basically two things you can do if the minerals have attached themselves to the glass. 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.

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.

Actually you can find all the supplies online at a window cleaning supply house like ABC Window Cleaning Supply or J. Racenstein.

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

Here's the mechanical link: http://tinyurl.com/38kbx7s

If you are trying to remove the stains from the masonry products, try a product like Eco-Wares Efflorescence Remover. You can find their website here: http://www.eco-wares.com/Cleaners_productdetail.html#efflorescence

After you have removed the stains, you probably will want to put a sealant on your masonry products to keep this from happening again. You might try Trojan Masonry Sealer or Chemprobe Prime-A-Pell 200.


Let me know how things turn out.

Sincerely,

Robert Lamb

270-704-9303
Window Masters
http://www.window-masters.com



---------- FOLLOW-UP ----------

QUESTION: Robert,
My aim is to remove stain from the glass but when I have this done I will then take your advice and seal the masonry at the window head. Can you give me a site to purchase the Trojan Masonry Sealer or Chemprobe Prime-A-Pell?
Brian

Answer
Brian,

Envirosafe is a manufacturer of environmentally safe concrete and masonry cleaners, sealers, degreasers, and coatings. You can order Trojan Masonry Sealer online at http://www.envirosafemfg.com/

Chemprobe Prime-A-Pell is a little harder to find. Some good paint stores carry it.


Let me know how your project is going.

Sincerely,

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