Fading colours and yellowing whites can occur under the influence of UV radiation if you opt for an inferior grade of uPVC. This usually happens when savings are made with the stabilisers that should be used to preserve the material's colours. Of course, you do not need to fear such negative outcomes with the branded products you can purchase from us. Nevertheless, you should regularly remove any dirt from the frames of your tilt and slide patio doors to stop it permanently burning into the material over time. You can also get special uPVC cleaners for this purpose that form a dirt-repellent protective film on the surface.