Usually, plastic windows are made of 2 or 3 glasses, which have a thickness of 4 millimeters. Let’s first consider a simple technique that makes it possible to determine how much glass in the double -glazed window. Modern plastic windows are so high and their transparency is so high that it is quite difficult to determine how much a glass in the eye is quite difficult. A simple technique is that you need to bring a light match to the window and calculate how many reflections the fire on the glasses has. If you can see two double reflections, then glass 2, if three double, then 3.