Traffic Film Taxonomy

The Urban Glaze

A house beside a main road, a roundabout or a motorway junction wears a coat that a house in a quiet cul-de-sac does not. It is grey, faintly oily to the touch, and it dulls everything it settles on: glass, uPVC, render, the paint on the front door. Residents rarely notice it arriving because it builds by microns a day. They notice it the first time a window is properly cleaned and the pane beside it suddenly looks brown.

What is Traffic Film?

Traffic film is not one substance but a settled mixture of everything a road produces. Unburnt and partly burnt fuel from exhausts. Carbon soot. Fine rubber worn from tyres. Iron and copper dust from brake pads. Road salt in winter. Bitumen dust from the surface itself. The exhaust fraction is oily and the metal and rubber fractions are fine enough to stay airborne, and together they form a hydrophobic layer that water alone will not shift.

A growing share of it now comes from brakes and tyres rather than tailpipes. The UK's Air Quality Expert Group has reported that brake, tyre and road wear now make up the majority of primary particulate from road transport, and an electric car sheds that particulate like any other. The film on a roadside house is not going away as the fleet changes.

Electrostatic Bonding

Fine particulates in the air carry a small electrical charge, and glass and plastic surfaces readily hold the opposite one. The result is that these particles are not merely deposited on a window; they are attracted to it and held. The oily fraction then does the rest, binding the dust into a continuous film that dries hard in the sun and resists rain.

uPVC is particularly prone to this because its surface is so easily charged, which is why the frames on a roadside house so often look worse than the glass they hold.

Why Pure Water Struggles

Pure water is our tool of choice for almost everything, and traffic film is where it meets its limit. Water is a polar solvent and oil is not, so on a heavy hydrocarbon film even deionised water beads up and runs off without lifting it. Light traffic film on regularly cleaned glass comes away with pure water and agitation. Heavy, baked-on film on neglected frames and render does not, and pretending otherwise leaves a customer with a wet, dirty house.

The SIM-Code Synergy

The most stubborn grime on urban render is not traffic film alone and not algae alone but the two grown together. The oily film provides a sticky anchor and, in its nitrogen and phosphorus content, a supply of nutrients. Algae colonise the film, bind it with their own gelatinous secretions, and trap further particulate as they grow. Within a few seasons the result is a dark, tough, layered composite that behaves like neither of its parents.

We record this combined state under its own code because it needs its own treatment: a degreasing stage to break the oil, followed by a biocidal stage to deal with the living component. Either alone leaves half the problem in place.

Alkaline Emulsification

Oil is removed with a surfactant. A traffic film remover is a mild alkaline detergent that surrounds the oil droplets, lifts them off the surface and holds them in suspension so they can be rinsed away rather than smeared around. Applied at low pressure, allowed a short dwell, agitated gently and rinsed thoroughly with pure water, it takes the film off glass, uPVC and painted surfaces without harming them.

The one caution is anodised aluminium. The protective oxide layer on anodised cladding and window frames is attacked by alkalis, so on those surfaces the chemistry is changed to a pH-neutral product and the dwell time shortened. Knowing which surface you are standing in front of is the whole job.

How to Identify It

A grey or brownish dullness that is worst on the side of the house facing the road and on the lower floors. Run a fingertip across a window frame: traffic film feels slightly greasy and leaves a grey smear. Spray a little water on the glass: on a heavy film, water beads and runs in trails instead of spreading into a sheet.

What It Is Not

Algae is green and grows in damp or shaded areas whether or not there is a road nearby. Chalking uPVC leaves white on your finger, not grey. Sooty mould under trees is black and patchy rather than an even film. Rain streaks from sills are localised, while traffic film covers the whole elevation.

Where to Look on Your Property

Road-facing elevations, especially near junctions, traffic lights, bus stops, speed bumps and hills, where vehicles brake and accelerate hardest. Ground and first floors take the most. Check garage doors, front doors, porches, uPVC frames and the fronts of conservatories, and the lower courses of render, which grey first.

What You Can Safely Do Yourself

On uPVC and painted surfaces, warm water with a little washing-up liquid on a soft cloth or sponge lifts a light film; rinse it off well. Don't use scourers, solvents or cream cleaners, and avoid strong degreasers on anodised aluminium or powder-coated frames. Don't pressure wash render to get the film off.

When to Call a Professional

For glass, which needs a careful detergent stage and a pure-water rinse to finish without spots; for render, where the film is often bound up with algae; and for anything above ground-floor height. Regular maintenance cleaning is far easier and cheaper than removing years of baked-on film in one go.

How to Keep It Away

You can't stop the traffic, but you can reduce what reaches the house. Research from the University of Surrey found that dense roadside hedges substantially reduced traffic particulates behind them, cutting black carbon by up to 63 per cent, with the strongest effect in summer when the hedge is in full leaf. A hedge between the road and the house protects the front of the building as well as the people inside it.

Beyond that, a steady cleaning interval stops the film baking on and keeps each clean quick.