Crown glass is an old type of glass used for making windows. It can still be found in some old houses or mansions built before the nineteenth century. The method originated in France, but was kept secret for centuries so it became popular in England only in the seventeenth century. The process of manufacture was quite complicated. First, glass was blown into a ball. Then the ball was flattened into a disc called bullion. Glass in this form was placed in a metal frame. At this point, new windows could be created. Windows of this kind look a bit peculiar. bullion is usually quite thick, the glass is much denser in the middle of the disc, and it is difficult the see through it. Sometimes it looks like a stained-glass window as it also has frames, but is not really ornamental and usually much less colourful. Today, this method is not widely used any more. Hand-made glass is not the most effective way of manufacturing windows. However, some artists still use some crown bullion glass elements in their work. Of course, there are not many specialists like that, but sometimes there is a need to hire somebody who has some experience in this type of glass making. Reconstructing famous historic building often requires returning to this old method.