Clean Windows Like a Professional

Dear James: My husband and I just moved into a new house. The windows were sparkling clean, but now I cannot eliminate streaks. Even my husband notices it. How do the professional builders clean the glass? — Pam H.

Dear Pam: If your husband commented on the streaky windows then you know that you must have a very serious dirty window problem.

Actually, your builder most likely hired a professional window washer to clean them when the construction was completed. For the first year or so, it is important to keep the window glass clean with proper cleaning techniques. Dust from cement, shingle granules, cutting tool blades, etc. will be present for quite a while after the house is completed. All of these materials are very abrasive, and they can damage the glass surface, and some can react chemically with it.

If you have ever watched a professional washer, you probably did not see him using a spray bottle and a roll of paper towels. This technique removes some of the abrasive dirt, but much of it is just spread in an even film over the glass. It may look fine at night, but when the sun hits it, it is a mess.

To really clean windows well, you must remove all the dirt and then rinse it thoroughly before you attempt to dry it off. A good quality squeegee and a lambswool-type scrubber are a must for a good job. A medium- to long-nap fleece scrubber is also effective for applying the soapy solution.

The key is to get the scrubber well saturated with the solution so that it picks up the majority of the dirt from the glass while also flooding and rinsing it. When it is squeegeed dry, only clean solution is being squeegeed off. Remember that glass is relatively soft and porous, so rubbing it hard with dirty paper towels can scratch and dull its surface over time.

If some of the glass windows still have some specks of cement, paint or tree sap on them, try using a “porcupine” scrubber. This type of scrubber has strong synthetic bristles with coarse ends. It will not scratch the glass, but it will dislodge the heavier dirt. A scraper will also help, but always use a new blade that has no burrs that may cause fine scratches on the glass.

Using the squeegee properly to remove the water is the final and most important step. Make sure to use a high-quality, professional squeegee with a brass body and replaceable rubber blades. Brass is a relatively soft metal, so it will not scratch the glass if you bump it. An 18-inch-wide one works best, but you might try a 12-inch squeegee first to get the hang of it.

The proper squeegee technique is a horizontal pass across the window starting at the top. Tilt the squeegee so that the water flows down on to the already-wet area below. After each stroke, wipe off the squeegee with a lint-free cloth (most paint stores sell these). Overlap each stroke by about two inches for the best results.

When you are done with the squeegee, use the lint-free cloth in a vertical direction down each edge of the glass to remove all the water. Another good tip is to never clean windows in the sun. The heat from the sun will cause the window to dry too fast to avoid streaks.

The following tools and materials make the job easier: lambswool scrubber, squeegee, lint-free rags, soap or detergent and water.

Send your questions to Here’s How, 6906 Royalgreen Dr., Cincinnati, OH 45244 or visit