I was sitting back looking through the large sliding glass windows on my porch and noticed they looked clean but they had “translucent  streaks” through them. Must be a fine dust or dirt I thought, so I grabbed the bottle of glass cleaners under the sink, containing the “powerful” window cleaning ingredients of vinegar and ammonia. Then I got a roll of paper towels and redid both sides of the glass. Easy. I sat back down and to my surprise, there were those streaks again – only more of them.

The secret

So the next time I walked by a professional window cleaner working her magic squeegee on a large retail window, I stopped her and asked her about my streaking problem.  She looked me up and down and said “I don’t know If I should tell you about streaking or not. It’s a trade secret.” After swearing to her that I would never clean a window for money for the foreseeable remainder of my life and besides I am afraid of heights – she looked me up and down again and came to a decision that this was probably true, especially the acrophobia part. “It’s grease” she said. “What?” I said. “It’s grease that is streaking your windows.” “But we never use grease on or around our windows”, I said. She just shrugged and said “Go home and instead of Windex, get your Dawn dishwashing detergent.” she turned and went back to work.

Professional window cleaning involves a systematic approach and specialized tools to achieve streak-free, sparkling results. This process (or approach) can involve the following:

Gathering equipment

This typically includes squeegees, scrubbers or applicators, scraper or razer blades, extension poles, buckets, the cleaning solution, towels or lint-free cloths, and sometimes ladders or scaffolding for reaching higher windows.

Prepping the Windows

Before starting the cleaning process, professionals inspect the windows for any stubborn dirt, debris, or residue, which they scrape off.

Applying the Cleaning Solution

Using a scrubber or applicator, the cleaning solution is applied evenly to the entire surface of the window.

Squeegeeing Technique: The squeegee is the key tool for achieving streak-free results. Professionals start at the top corner of the window and pull the squeegee across the glass in a smooth, overlapping motion, working from top to bottom. They wipe the blade clean after each stroke with a lint-free cloth or towel to prevent streaks and drips.

Detailing Edges and Corners

After squeegeeing the main surface of the window, professionals use a smaller squeegee or cloth to clean the edges, corners, and any remaining water spots or streaks.

Drying and Polishing: To finish, professionals use a dry, lint-free cloth or towel to wipe away any remaining moisture and polish the glass to a sparkling shine. They may also inspect the windows from different angles to ensure they are completely streak-free.

Cleaning windows effectively is best left to professionals. LACOSTA professionals are well-versed in various cleaning techniques, and most are not afraid of heights. Nevertheless,  I now use Joy liquid dishwashing soap and water to clean my sliding door window at home.