The rear windows in a soft-top convertible can either be glass or plastic. The latter must be treated with care if it is going to last as long as the hood it is attached to. This is particularly important as Scratches and discoloration do not only look bad, they can also distort rearward visibility.
Damage can come from a number of different causes. Sunlight and more specifically ultraviolet light (UV) can cause yellowing and clouding of plastic windows. Over time UV can also cause the window to become brittle eventually leading to splits. Unfortunately the only way to reduce any of this is to keep your car out of the sun; not always a practical reality. However preventing scratches and creases is easily done.
Much of the scratching seen on plastic windows is actually caused by incorrect cleaning. When a dirty window is cleaned the dirt particles can be dragged across the surface cutting into it in the process. This can be reduced by first soaking the surface with water to soften the dirt.
The window can then be washed with clean water or if needed, a mild detergent. Be gentle and only use a cleaning product that is recommended for plastic windows and doesn’t contain any harsh chemicals which could degrade the material. To avoid scratches a sheepskin or synthetic washmit pulls the dirt away from the surface unlike sponges which can trap grit against the plastic. Dry the window with a clean cotton cloth.
Finally, in day to day operation of your roof it’s important to ensure that when the roof is folded down the window folds cleanly and without any awkward creases. Particular care should be made in cold weather. When the plastic is cold it is far more brittle and more likely to split. Scratches are often caused when a dirty window folds against itself, sandwiching the abrasive dirt in between, so try to only fold your roof down when the window is clean. One tip I have heard is to place a clean towel over the plastic before folding the top down.
If the surface has scratches already then these can often be repaired near to their original transparency with a specialist plastic polish. Care must be taken if using a polish to be sure the window is completely clean or you will only add to the scratching. It will need some hard work, however don’t use an electric polisher as this may be too harsh for the delicate plastic surface.
If a plastic window is beyond repair then it may be possible to replace it. Some windows can be zipped out, others can also be replaced by a specialist. Main dealers may be able to offer this service, however their prices can be very high and they may.
When treated with care a plastic window will last as long as your convertible top and offer many years of happy motoring.