If you have ever cleaned your windows on a bright day and watched them dry streaky an hour later, you are not alone. Coastal glass picks up a fine film of salt and traffic grime that ordinary washing smears around rather than removes. Here is why it happens and how professional methods deal with it.
What that film on coastal glass actually is
Sea spray carries dissolved salts that settle on glass as microscopic crystals, and on top of that comes pollen, traffic film and the general dust of everyday weather. Washing-up liquid and a cloth will move this around, but as the water evaporates the dissolved minerals dry back onto the pane, which is exactly the streaking most people fight with.
Why pure water systems work
Professional reach-and-wash systems filter tap water until it contains virtually no dissolved solids. Glass scrubbed and rinsed with pure water dries spotless because there is nothing left in the droplets to dry onto the pane. It also means frames, sills and upper-floor windows can be cleaned safely from the ground.
The first pure-water clean on long-neglected glass can occasionally show residual spotting as embedded grime keeps leaching out; a follow-up visit settles it. This is normal and any honest window cleaner will mention it up front.
Looking after uPVC frames between visits
White uPVC dulls and greys as airborne grime bonds to the surface. Regular washing as part of a window round keeps it bright; what damages it is abrasive pads, solvent cleaners and pressure washing at close range, all of which can permanently scratch or matt the finish. If frames have already yellowed with age rather than dirt, cleaning improves but cannot fully reverse it, and it is worth knowing that before paying anyone for a miracle.
How often is worth it
Most homes on our rounds choose a four to eight week cycle, which keeps glass consistently clear rather than swinging between sparkling and grimy. Shopfronts facing the street usually justify a more frequent schedule because first impressions drive footfall.