High Quality Content by WIKIPEDIA articles! The term Forest glass or the German name Waldglas is given to late Medieval glass produced in North-Western 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 characterised by a variety of greenish-yellow colours, 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 centred around the Mediterranean and contemporaneous Islamic glass making to the east.