WATCH YOUR GLASS

1. Dirt removal is crucial. Professionals sweep the entire area first, including the tracks and sills, with a hand brush.

2. Using glass cleaner and paper towels won’t get you professional results. You’re just spreading the dirt around; you’re not lifting the dirt off the glass. Pros use special glass cleaner (not Windex) or a small quantity of a grease-cutting dish soap such as Dawn. Everyone swears by their own solution. (Either way, you’re not looking for a lot of suds.) Skip the vinegar and water, says Autery. He points out the mess that newspaper ink makes, the way vinegar smells and the fact that even amateurs have access to better products.

3. The squeegee moves everything off the glass to the point where you can remove it. If you’re getting a line or streak, it means the rubber is bad or old or you have a bad squeegee technique. “It’s all about keeping the blade on the glass,” says Burkett.

4. You have to wipe off the squeegee blade after each pass, using something lint-free and absorbent. You also have to wipe the excess water off the edge of the window.

5. Tinted windows cannot take ammonia.

6. Windows that haven’t been cleaned in a long time require more work. And nicotine is a bear to remove. Professionals use quadruple (0000) steel wool to avoid scratching the glass and/or razor blades to get off paint, stubborn gunk and other dirt the scrubber misses. This is where it gets tricky. If you don’t know what you’re doing, you can scratch the glass. Also, tempered glass is more prone to scratches. You can also cut yourself.

7. Avoid washing windows in direct sunlight if possible; sun evaporates the water too quickly.

8. Hard water and chlorine can etch your glass. This is why your shower door and the doors near your swimming pool never look clean.