For example, when low -quality titanium oxide is added to the mixture, the windows from such PVC in a couple of years acquire a yellow tint. This is due to the fact that this component goes through several stages of cleaning, which is very expensive. Poorly purified Titan oxide begins to darken over time. In addition, high -strength components are added to the profiles, designed to protect the finished product from strokes. It is important to distribute all these components in the mixture evenly, as well as cool using a special technology.