Streaks come from cleaning solution drying on the glass before it is removed, not from the glass being dirty. The three usual causes are working in direct sunlight, using too much soap, and wiping with a cloth that is already saturated. Fix those three and most streaking disappears.
This is the most common complaint we hear from homeowners who have just spent an afternoon doing their own windows. The glass is clean. It just does not look clean, and it looks worse in the exact light you were trying to improve.
Why streaks happen at all
A streak is a thin film of residue. Something was on the glass, it got wet, and then the water evaporated before anything removed it. What is left is whatever was dissolved in that water: soap, minerals, dirt, or all three, redistributed into a pattern you can see in raking light.
That is why streaks show up on sunny days and on clean glass. Sun accelerates evaporation, and a dirty window hides residue that a clean one shows off.
The five most common causes
1. Cleaning in direct sun
This is the big one. On a warm sunny day the solution starts drying the moment it touches the pane, and you are working against a clock you cannot beat. Work on the shaded side of the house and follow the shade around as the day moves.
2. Too much soap
Almost everyone overdoes this. More soap does not clean better, it just leaves more residue for you to remove. Professionals use surprisingly little, often a few drops in a gallon. The soap is there to lubricate the squeegee, not to dissolve the dirt.
3. A saturated cloth
Once your towel is wet, it stops absorbing and starts spreading. If you are wiping and the streaks are moving around rather than disappearing, your cloth is done. Have several, and swap early.
4. A dirty or nicked squeegee blade
Rubber picks up grit. A blade with a nick in it will leave a line down every pane, in the same place, and you will chase it until you look at the blade. Wipe the blade after each pull, and replace it when it stops being sharp at the edge.
5. Ignoring the frame
You can clean the glass perfectly and still get streaks, because dirty water sitting in the frame runs back down onto the pane as soon as you finish. The frame has to be wiped before the glass is dried, not after.
The order professionals work in
Sequence matters more than product. This is roughly how the job goes:
- Dry brush or vacuum the frame and sill, so loose grit is gone before water is introduced.
- Wash the glass with a lightly soaped scrubber, working edge to edge.
- Squeegee immediately, in overlapping passes, wiping the blade between each one.
- Detail the edges and corners with a dry cloth.
- Wipe the frame and sill last, so nothing drips back onto finished glass.
Notice that drying is not a separate step at the end. The pane gets dried as it is washed, one window at a time. Washing five windows and then going back to dry them is how most home cleaning goes wrong.
Tools that matter, and one myth
A real squeegee with a fresh rubber blade will outperform any spray and paper towel combination, on any glass, every time. It is the single upgrade worth making.
Microfiber is genuinely better than cotton for detailing because it absorbs rather than pushes. Paper towels shed lint onto clean glass and fall apart when wet.
As for cleaning windows with newspaper: it worked when newsprint used oil based inks and rag content paper, which has not been true for decades. Modern newspaper is softer, the ink transfers, and you get grey smudges on your frames. It is a piece of advice that outlived the product it was written about.
When streaks are not streaks
Sometimes the marks will not come off no matter what you do, because they are not on the surface you are cleaning.
| What you see | What it probably is | Can cleaning fix it? |
|---|---|---|
| Cloudiness that stays visible when the glass is wet | Mineral etching in the glass surface | No, the pane needs replacing |
| Haze between the panes that you cannot reach from either side | Failed insulated glass seal | No, this is a glazing repair |
| Fine scratches in one direction | Something abrasive was used previously | No |
| Marks only on the outside, worst at the bottom | Hard water deposits from sprinklers | Usually yes, with an acidic mineral remover |
| Rainbow sheen that shifts as you move | Residue film, often from old cleaner buildup | Yes |
The wet test sorts most of this out. Spray the pane and look at it while it is wet. Anything that disappears when wet is removable. Anything still visible is in the glass, not on it. If the marks are worst on the lower outside panes, you are probably looking at hard water deposits rather than streaks.
Frequently asked questions
Why are my windows streaky after cleaning them with Windex?
Ammonia based sprays evaporate fast and are usually applied far more heavily than needed. On a warm day the product is drying while you are still wiping, which leaves exactly the residue you are trying to remove.
What is the best solution for streak free windows?
Warm water with a few drops of dish soap, applied with a scrubber and removed with a squeegee. The solution matters far less than the technique and the timing.
Should I clean windows on a cloudy day?
Yes. Overcast and cool is close to ideal because the solution stays wet long enough for you to remove it properly.
Why do my windows streak on the inside but not the outside?
Interior glass usually carries an oily film from cooking, heating and hands, which needs more agitation than a quick wipe. It also gets cleaned more often with spray products, so residue builds up in layers.
If you would rather not chase it
There is no trick to this, just sequence, timing and the right blade. If that sounds like a Saturday you would rather have back, Clearwater Window Cleaning is owner operated and serves Carmel, Fishers, Westfield and Noblesville. See what a residential window cleaning covers, or call or text (317) 502-8135.
