Glass is a liquid-type (as opposed to crystalline) material that is formed when silica is mixed with other compounds - typically soda (sodium bicarbonate) and lime (calcium carbonate) - and heated to beyond melting point before being cooled rapidly. Man made glass - as opposed to naturally occuring fusions of calciferous sand and soda, for example during volcanic activity - dates back to at least 3500 BC, with the remains of non-transparent glass beads found in Egypt and Eastern Mesopotamia. There is also evidence of other ancient glassmaking activities emerging independently in Greece and China. The earliest examples of Egyptian glassware are three vases bearing the name of the Pharaoh Thoutmosis III (1504-1450 BC), who is said to have brought glassmakers to Egypt as prisoners following a successful military campaign in Asia. The technique of glass blowing has been traced back to Syrian craftsman in the Sidon-Babylon area around the time 27BC and 14AD. Towards the end of the last century BC the ancient Romans also began blowing glass inside moulds, a technique that allowed a variety of shapes to be made in hollow glass items. These early glassmaking techniques were spread by the Romans across their burgeoning empire and as far as China, shipped along the silk routes. It was during the Roman era that eastern and western glass craftsmen began to develop distinct differences in their wares, with the east - centred around Alexandria - producing luxury items primarily for export and the west - with a hub at Koln - making less ornate glassware. Another major geographic difference occured towards the turn of the millennium (1000AD), when the raw material soda ash was replaced in northern European regions (north of the Alps) by potash made from the burning of trees. In the Mediterranean areas such as Italy, they continued to use soda ash. The first evidence of sheet glass production comes from Germany in the 11th century, and their technique was further developed by Venetian craftsmen in the 13th century. The technique involved spinning or rolling out a ball of molten glass that had been blown. By using lead strips to connect these relatively small sized panes, a larger window could be created. In the Middle Ages the city of Venice assumed its role as the glassmaking centre of the western world. The Venetian merchant fleet ruled the Mediterranean waves and helped supply Venice's glass craftsmen with the technical know-how of their counterparts in Syria, and with the artistic influence of Islam. The importance of the glass industry in Venice can be seen not only in the number of craftsmen at work there (more than 8,000 at one point). A 1271 ordinance, a type of glass sector statute, laid down certain protectionist measures such as a ban on imports of foreign glass and a ban on foreign glassmakers who wished to work in Venice: non-Venetian craftsmen were themselves clearly sufficiently skilled to pose a threat. Until the end of the 13th century, most glassmaking in Venice took place in the city itself. However, the frequent fires caused by the furnaces led the city authorities, in 1291, to order the transfer of glassmaking to the island of Murano. The measure also made it easier for the city to keep an eye on what was one of its main assets, ensuring that no glassmaking skills or secrets were exported. In the 14th century, another important Italian glassmaking industry developed at Altare, near Genoa. Its importance lies largely in the fact that it was not subject to the strict statutes of Venice as regards the exporting of glass working skills. Thus, during the 16th century, craftsmen from Altare helped extend the new styles and techniques of Italian glass to other parts of Europe, particularly France. In the second half of the 15th century, the craftsmen of Murano started using quartz sand and potash made from sea plants to produce particularly pure crystal. By the end of the 16th century, 3,000 of the island's 7,000 inhabitants were involved in some way in the glassmaking industry. A further landmark innovation in the history of glass and crystal was the development of lead crystal, which has been attributed to the English glassmaker George Ravenscroft (1618-1681). He patented his new glass in 1674 after he had been commissioned to find a substitute for the Venetian crystal produced in Murano and which was based on pure quartz sand and potash. By using higher proportions of lead oxide instead of potash, he succeeded in producing a brilliant glass with a high refractive index which was very well suited for deep cutting and engraving. In the 17th Century France took steps to promote its own glass industry and attract glass experts from Venice; not an easy move for Venetians keen on exporting their abilities and know-how, given the history of discouragement of such behaviour (at one point, Venetian glass craftsmen faced death threats if they disclosed glassmaking secrets or took their skills abroad). The French court, for its part, placed heavy duties on glass imports and offered Venetian glassmakers a number of incentives including French nationality after eight years and total exemption from taxes. In England the glass industry had a heartland in the midlands and particularly around the town of Stourbridge. During the 17th Century refugee 'gentlemen glass makers' from Lorraine in France settled there, attracted by the abundant supplies of coal and clay for their melting pots. Following the invention of lead glass, they began producing the tableware and ornamental glass for which Stourbridge became world-famous. The 19th century was the golden age of glassmaking in Stourbridge, with many new firms established and new colours and decorating techniques pioneered locally. Only a few of these factories survived in Stourbridge to the 21st century, and then often with a number of changes to the company names. The survivors include Royal Brierley Crystal, Royal Doulton Crystal and Stuart Crystal.
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