You have just had your windows cleaned. They look great. Two weeks later, they look dirty again. Is that normal? Is something wrong? Here is the science behind why windows get dirty — and what actually makes a difference.
The main culprits
Windows collect dirt from multiple sources simultaneously:
- Airborne dust and pollution — fine particles in the air settle on glass continuously
- Rain — not as clean as it looks, rain carries dissolved atmospheric pollutants and, in Norfolk, often agricultural dust
- Bird droppings — highly acidic and bond quickly to glass
- Pollen — particularly heavy in spring and early summer
- Road spray — properties near busy roads get a fine mist of dirty water
Does cleaning method affect how long they stay clean?
Yes, significantly. Traditional tap-water cleaning leaves mineral residue on the glass. That residue is slightly sticky and attracts new airborne particles more readily than clean glass. Pure water cleaning leaves no residue, so windows cleaned with pure water stay cleaner for longer.
Environmental factors matter
Properties on main roads or near farmland will always accumulate dirt faster than those in quieter locations. There is nothing wrong with the cleaning — the environment is simply more aggressive.
What about after rain?
Pure water-cleaned windows generally look fine after rain. The glass is clean, so water sheets off rather than sitting in pools and drying with spots. Tap-water-cleaned windows, by contrast, often look worse after rain because water clings to the mineral residue.
The honest answer
Some re-soiling within two to four weeks is normal for any property in an active environment. A regular cleaning schedule — every four to eight weeks — is the practical solution. It is cheaper per visit and keeps your windows consistently clean rather than very dirty most of the time.