The short answer: what professionals actually do
Most professional window cleaners use a surprisingly simple approach. They wash the glass with a soft applicator and a bucket of water with a small amount of dish soap, then remove the water with a rubber squeegee, and finish by wiping the edges with a lint-free cloth. The skill is mostly in the technique and in having tools that do the job quickly, rather than in a secret cleaning product.
You can copy the same method at home with fairly modest equipment. The steps below follow what professionals commonly describe, adapted for a homeowner.
Safety first
Before you start, a few precautions matter more than any technique:
- Never mix cleaning products. Do not combine bleach with ammonia (found in some glass cleaners) or with vinegar or other acids. These combinations can release toxic gases. Use one product at a time, rinse surfaces between products, and keep the room ventilated. If you are unsure what a product contains, check the label and do not combine it with anything else.
- Take ladders seriously. Falls from ladders cause real injuries. Use a stable ladder on firm, level ground, keep three points of contact where you can, and do not overreach. For upper-storey or hard-to-reach windows, consider a pole system or hiring a professional.
- Protect children and pets. Keep them out of the area while you work. Store cleaners, scrapers and razor blades out of reach, and let floors and sills dry before they return, since spilled solution can be slippery and some products are harmful if swallowed or licked.
- Handle scrapers carefully. A blade is sharp. Cover it when it is not in use.
The professional toolkit
Professional kits vary, but they tend to include the following:
- A squeegee with a good channel and a fresh rubber blade. The blade does most of the work, so a nicked or hardened blade leaves streaks.
- A washer or scrubber (often a microfiber sleeve on a T-bar handle) or a natural sponge to apply the solution.
- A bucket of clean water with a small amount of mild dish soap.
- A scraper for dried paint, sticker residue or similar debris, used with care.
- Lint-free detail cloths, such as microfiber, for edges and the final wipe.
- Drop cloths or towels to protect floors and sills indoors.
- A small brush for window tracks and corners.
For tall buildings, commercial crews often use water-fed or “reach and wash” pole systems that allow them to clean from the ground, or access equipment such as lifts for higher glass. That is generally not a household job.
Step-by-step: the professional method
Prep the frame, tracks and sills
Professionals typically start with the surroundings, not the glass. Remove or open screens, and move blinds and curtains out of the way. Brush loose dirt and cobwebs from tracks and frames, and vacuum the debris. Wipe the frame and sill so that dirty water from the frame does not run onto clean glass later. Indoors, lay a drop cloth to catch drips.
Wash the glass
Dip the washer or sponge in the soapy water and wring it out so it is wet but not dripping. Scrub the whole pane, paying attention to bug spots, pollen and greasy marks. The goal is to loosen all the dirt so the squeegee can lift it away with the water.
If you find dried paint or sticky residue, hold a scraper at a low angle against wet glass and use light pressure. Test in a small corner first, and avoid scraping glass that has a film, coating or etched surface, since it may be damaged.
Squeegee: horizontal, vertical and S-stroke
Squeegee technique is the part that takes practice. A few common approaches:
- Horizontal passes. Hold the squeegee at a slight angle to the glass and pull across from one side to the other, overlapping the previous pass slightly.
- Vertical passes. Make a dry edge along the top with a cloth or the end of the squeegee, set the blade on that edge, and pull straight down.
- S-stroke or fan. Many professionals pull the squeegee across the glass in a continuous S-shape, which keeps the blade moving and guides water down the glass without leaving lines.
Whichever you use, wipe the rubber blade with a dry cloth after each pass. A wet or dirty blade is a common cause of streaks.
Detail the edges
Wrap a dry, lint-free cloth around your finger and wipe the water line left around the perimeter of the glass and any drips on the frame. This final detailing is a large part of why professionally cleaned windows look finished.
Why pros avoid paper towels and newspaper
Many cleaning guides still suggest paper towels or newspaper. Professionals tend to avoid them for a few reasons. Wiping with paper can push dirt around rather than remove it, and it may leave lint. One window-cleaning professional quoted by This Old House also notes that heavy rubbing can build up a static charge that attracts dust. Lint-free microfiber cloths are generally the better choice for detail work.
Timing and weather
Direct sun dries the solution before you can squeegee it, which leads to streaks. An overcast, calm day is often easier because the solution stays wet longer and spray is less likely to blow back at you. If you must clean in sun, work on one window at a time, or do the shaded side of the house first.
Windows with divided panes and high windows
Windows with many small panes (muntins) are slower. Use a smaller squeegee or a cloth held at the bottom of the blade to catch water and protect wood dividers from excess moisture. For windows that are too high to reach safely, use an extension pole with a washer and squeegee head, or hire a professional rather than climbing.
What should you not use to clean windows?
It helps to know what to avoid:
- Abrasive scrubbers or steel wool, which scratch glass.
- Paper towels and newspaper for the final wipe, for the reasons above.
- Too much soap. Extra dish soap leaves film that causes streaks. A few drops in a bucket is enough.
- Mixed chemicals. Never combine bleach, ammonia and vinegar. See the safety section.
- Harsh products on coated, tinted or specialty glass. Check the window manufacturer’s care instructions first.
- Dirty or damaged squeegee blades.
Related jobs
Windows are rarely just glass. If your screens are grimy, see our guide to the best way to clean window screens. For glass above your head, our article on how to clean a skylight from inside covers safe reach and drip control. Textured panels need a different approach, explained in how to clean the rough side of frosted glass.
How much does professional window cleaning cost?
Prices vary widely by region, the number and size of windows, how many storeys the home has, how dirty the glass is, and whether screens and tracks are included. Many companies quote per window or per job, and some have a minimum charge. Because costs differ so much, the most reliable approach is to request quotes from a few local, insured companies and ask exactly what is included.
When to hire a professional
Consider hiring help if windows are on upper floors or otherwise hard to reach, if you have large panes or many windows, if the glass has hard-water damage or heavy paint, or if you are not comfortable working at height. Ask about insurance and how they protect floors and frames.
FAQ
What is the 20 minute rule in cleaning?
There is no single standard definition, and it is not specific to windows. It usually refers to the idea of tackling a task in short, timed bursts, or of tidying for about 20 minutes a day, to keep chores manageable. If you want to apply it to windows, you could clean one or two windows per session rather than the whole house at once. For more on timed cleaning, see how to clean your house in 2 hours.
What are the 5 basic cleaning principles?
Definitions vary by source. Common themes include working from top to bottom, removing loose dust and debris before wet cleaning, using the mildest effective product, letting products work for the time recommended on the label, and drying surfaces. For windows, that translates to cleaning frames before glass and using minimal soap.