Broad sheet glass is a type of hand-blown glass.
It was invented in the 13th century in England. The manufacturing process is as follows: “Molten glass is gathered on a blowpipe, and blown to an elongated balloon shape. The ends are cut off and the resulting cylinder is split with shears while still hot, then flattened on an iron plate.” “Manufacture slowly decreased and ceased by the early 16th century.” Due to the relatively small sizes blown, broad sheet was typically made into leadlights. The centerpiece was used in places where looking through the glass was not important. If the piece was large, it was possible to see bubble tracks and strain lines.