This is an old film made with the co-operation of James Powell and sons ( Whitefriars ) circa 1938 A video of this film was made a few years ago but it is no longer available. This video is not a copy but has been made from an original source. It has been made for the enjoyment of all lovers of Stained Glass . Regards PatrickThere were 8 or 10 of these pots arranged in a cicle around a furnace. The pots holding the molten glass were changed every 2 or 3 weeks .