Why Do UPVC Window Frames Go Yellow, and Can It Be Fixed?

The Direct Answer

White UPVC window frames go yellow mainly from UV exposure breaking down the surface finish over years, combined with traffic film and general grime that builds up in that roughened surface once it starts. South-facing frames and frames on busier roads go first. It can usually be cleaned back a long way with the right products, but it is far easier to stop it getting that bad in the first place than to reverse it once it has.

What actually causes it

• UV breakdown. Sunlight slowly degrades the outer layer of the UPVC, which is what gives yellowed frames that slightly chalky feel.
• Traffic film. Road grime settles into that roughened surface and darkens the yellowing further, especially on frames facing a busy road.
• Being ignored. Frames get wiped around when the glass is cleaned but rarely get the same attention as the pane itself, so grime has years to build up.

Why regular cleaning matters more than people think

Every visit, we clean frames and sills with the same pure water used on the glass, not just the panes. That stops grime building up in the surface in the first place, which is the single biggest factor in how bad the yellowing gets over time. A frame that gets cleaned every four to eight weeks for years looks completely different to one that only gets wiped occasionally.

FAQ: Can yellowed frames be brought back to white?

Often a long way, yes, with the right dedicated UPVC restorer. How far depends on how long it has been left and how much UV damage has already happened underneath the grime.

FAQ: Is this included in a normal window clean?

Frames and sills are cleaned with pure water on every single visit as standard. Full detail is on the window cleaning page.

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