Forest glass

Forest glass (Waldglas in German) is late Medieval glass produced in North-Western and Central Europe from about 1000-1700 AD using wood ash and sand as the main raw materials and made in factories known as glass-houses in forest areas. It is characterized by a variety of greenish-yellow colors, the earlier products being often of crude design and poor quality, and was used mainly for everyday vessels and increasingly for ecclesiastical stained glass windows. Its composition and manufacture contrast sharply with Roman and pre-Roman glass making centered on the Mediterranean and contemporaneous Islamic glass making to the east.