7 min read · Updated September 2026
Why windows streak
Streaking has four common causes: cleaning in direct sun so the solution dries before it is removed, using too much detergent, using paper towel or a cotton rag that sheds lint, and re-wetting a dirty squeegee blade so soil is dragged back across the glass.
Fix those four and the glass comes clean with almost no effort. Professional window cleaners rarely use spray-and-wipe on large panes at all — they flood the glass, break the soil, and pull it off in one pass.
What you need
- A squeegee with a fresh rubber blade (replace it the moment it nicks)
- A washer or strip applicator, not a sponge
- A bucket of cool water with a few drops of dish soap — that is the whole solution
- Two clean microfibre cloths: one damp for edges, one dry for detailing
- A scraper blade for paint specks and adhesive, used only on wet glass
The step-by-step method
On smaller panes, a straight-pull technique works better than the S-pattern: pull top to bottom in overlapping vertical strokes, wiping the blade between each.
- Work in shade or early morning so the glass stays wet through the pass.
- Wet the whole pane with the washer and scrub edge to edge, including corners.
- Scrape off any bonded debris while the glass is still wet.
- Squeegee in a single continuous S-pattern from top to bottom, keeping the blade on the glass.
- Wipe the blade on a dry cloth after every pass — not on your sleeve.
- Detail the perimeter and sill with a dry microfibre, never with paper towel.
Common mistakes
| Mistake | What it causes | Fix |
|---|---|---|
| Too much soap | Film and hazing as it dries | A few drops per bucket is enough |
| Cleaning in direct sun | Dried solution and hard streaks | Work shaded side first, early morning |
| Paper towel | Lint and smearing | Use flat-weave microfibre |
| Worn squeegee blade | Thin lines on every pass | Replace the rubber, not the handle |
| Dirty water | Redepositing soil | Change water when it greys |
When commercial glass needs a professional
Interior glass up to arm's reach is reasonable in-house work. Beyond that the economics change quickly: anything above ground level requires fall protection and insurance, and hard-water staining, construction overspray, and mineral etching need restoration chemistry rather than soap and water.
For storefronts and offices across the GTA, most clients schedule interior and exterior glass monthly or quarterly, with entrance glass wiped daily as part of the janitorial program.
Frequently asked questions
Does vinegar clean windows better?
Vinegar works on light soil, but on commercial glass with grease or road film a few drops of dish soap in cool water outperforms it and rinses cleaner.
Why do my windows streak after I dry them?
Almost always the cloth. Paper towel and cotton leave lint and residue — a flat-weave microfibre used dry does not.
How often should commercial windows be cleaned?
Storefront glass typically monthly, office exteriors quarterly to semi-annually, and entrance glass daily as part of routine cleaning.
Can hard water stains be removed from glass?
Light mineral deposits usually can with an acidic restoration product. Etched glass cannot be cleaned — it has to be polished or replaced.