Some older uPVC window frames may lose their shine because of a build-up of dirt and grime on their surface. The best way to whiten uPVC window frames is to use a good quality crème cleaner available from most installers.

For regular cleaning of your windows, you can simply use normal soap and water - kitchen soap is fine for this purpose - as it will loosen the majority of grime allowing you to rinse it away.

Unlike painted timer and aluminium window frames, you do not need to worry about stripping paint away from the finish as the colour is applied all the way through the frame material, although you should avoid using abrasive cleaning products as these may spoil the surface of the frame and lead to patches.

If you find that there is significant staining on the frame that do not respond to soap and water, then consider using a light creme cleaner that will help to clean below the surface level.  You should avoid using any solvent based products on your windows as these can attack the plastic.