Expert: Robert Lamb - 1/9/2012

Question
Can you recommend a product and technique for cleaning windows that won't leave streaks? I spray on Windex, leave 1-2 minutes, wipe in one direction with terry or cotton cloths, or soft paper towels. Then I wipe the other direction (at right angle to the first wiping). And I get - streaks!

Thanks

Jo

Answer
Jo,

The short answer is to NOT use Windex. The long answer?

You are now 'enrolled' in my Window Cleaning 101 class. Please carefully read the paragraph below that starts with a warning.

Make sure you have a good window cleaning squeegee. You'll need the kind used by window cleaning professionals, not the kind used to clean automobile glass. You can find a professional window cleaning squeegee at a Home Depot or similar store. Unger and Ettore make these squeegees and are the name brand most commonly found. Also, make sure you use a new rubber blade as an old blade is sure to have nicks and cracks in it and will leave streaks on your windows. If you can't change the rubber blade in your squeegee, you don't have the right kind of squeegee.

Next you need a good window cleaning solution and a lint free cloth. If you have something stuck to your windows that is hard to remove, paint for instance, you can use triple fine steel wool or a new safety razor.

About steel wool: Steel wool is graded by its abrasive properties. You will be able to tell what kind you have, from grade 1-4, by the zeros on the packaging. Do not use "0" or "00" grade steel wool as they are too coarse. On the other hand, "000" or triple fine and "0000" steel wool will work just fine. I would recommend the triple fine as "0000" will quickly crumble and make more of a mess than it is worth. Also never use rusty steel wool. The reasoning behind all of this is based on the Mohs scale. Mohs rates the "hardness" of a mineral, in this case silica (the main ingredient in glass) as opposed to iron (steel wool in this case). Look it up if you want to know more about this, or just trust my 20 + years of experience.

WARNING! Most window glass found in homes today is "float glass" and is processed by highly trained individuals in a plant that has high standards. Some tempered glass, though, comes from temperers that have little regard for the public. Professional window cleaners, are constantly finding tempered glass in residential and commercial applications that have fabricating debris baked into the glass. This debris is usually microscopic and is only discovered when a window cleaning razor (and sometimes steel wool) is run across the glass during the cleaning process. When this happens and fabricating debris is present, the debris will break off, get caught under the razor or steel wool and then cause micro fine scratches in the glass you are trying to clean. This would only happen if the glass has not been cleaned properly before it has been tempered. Tempered glass is typically used in areas where there is a danger of the glass breaking. For example, it should be in all glass doors, and in large plate glass, like picture windows. If you are unsure if your glass is tempered or not, you can look in one corner of the glass for a small sandblasted logo that is supposed to be applied by the temperer. It is very difficult though to know if the glass has fabricating debris baked into it or not until the cleaning is underway and sometimes the damage is already done. One indicator that it is present is if when running a razor blade over the glass, you hear a slight hissing or crackeling noise. If there is no debris present, there should be no noise associated with running the razor over the glass. So if you think you are working with tempered glass, you might listen for this sound by testing the glass in an out of the way place.

Now for the window cleaning solution. Water is a great solvent. If you add a few drops of dish washing detergent in a pail of warm water you have your basic window cleaning solution. If the windows have any oily residue on them, and you will sometimes find this in new construction, you need to add a little ammonia. The correct proportions of these ingredients? Less is better! Use about 1/2 teaspoon of detergent to 5 gallons of hot water. If you use the ammonia, you will only need 1/4 cup to 5 gallons of water. In my humble opinion, this works far better than the "blue stuff"! Add your detergent to your water, not the other way around or you will have far too many bubbles. What kind of dish washing detergent? It doesn't really matter. My personal favorite is Dawn or Joy.

Now all you need is a lint free cloth. You can use the micro fiber cloth if you want. There are other kinds that also work well. I personally like huck towels that can be ordered from a window cleaning distributor.  

The method to clean the window is to dip a sponge (or brush) into the 5 gallon of window cleaning solution and "scrub the window with it. (By the way, there is a special tool made for this, a T bar, but you don't really have to have it.) For any hard to remove spots, just break out the steel wool or safety razor while the window is still wet. It is recommended to use these tools in one straight pass followed by the next straight pass. In other words, don't use your razor or steel wool as though you were buffing the window in circular or back and forth motions. If there is any debris on the window that kind of motion will only catch the debris and cause it to scratch the windows.

Finally, holding your professional squeegee vertical, wipe a clean, dry swath across your window, wiping the squeegee dry after each pass. On the following pass and thereafter, overlap your swaths by 1/4 of an inch and finish by detailing with your lint free cloth.

You may find it helpful to pre-detail by using your cloth to wipe around the top and sides of the wet window before you squeegee.

These are basic and simplified directions. There are more finer points that I can share with you if needed.

Please let me know how the windows come clean after following these directions!

Sincerely,

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