Streak-free glass comes down to four things: a clean, unnicked squeegee rubber, very little detergent, working out of direct sunlight, and not drying the pane with a cloth. Streaks are almost never a technique problem — they are something being left on the glass, and there are only a few candidates.
The four causes, in order of likelihood
- The rubber. A worn edge pushes a film of water instead of cutting it off, and a single nick draws a line down every pane. Wipe the blade after every stroke and replace the rubber when it stops leaving glass dry in one pass — a 71cm replacement is R109.
- Too much detergent. Soap that is not fully removed dries as a film and attracts dust within days. A few drops in a bucket is enough; the washer does the work, not the chemistry.
- Direct sunlight. Solution that dries before you can pull it off leaves exactly what you were trying to remove. Follow the shade around the building.
- Drying with a cloth. A cloth reintroduces lint and redeposits dirty water. Use it only to detail the perimeter bead, never across the pane.
The stroke
Start at a top corner, pull steadily across at a shallow angle, and overlap each pass by two or three centimetres into the already-dry area. Wipe the blade between strokes. Consistent speed matters more than pressure — pressing harder bows the channel and lifts the blade edge in the middle, which is what produces a stripe straight down the centre of the pane.
The professional answer: no drying at all
Purified water below 10 ppm of dissolved solids dries leaving nothing, so there is no squeegee stroke to get wrong and no cloth to leave lint. That is how high windows are cleaned streak-free from the ground — see what water window cleaners use. A TDS meter at R290 tells you whether your water is actually pure enough; if it reads above 20 ppm, the water itself is your streaks.
Streaks that will not come off
If the marks resist everything, they may not be on the glass. Hard water run-off from sprinklers etches the surface over time, and that is permanent. Builder’s residue and paint need a scraper at R270, used wet and at a shallow angle.
See the full window cleaning equipment range.