Piece of Ancient Egyptian frit, found in the Theban necropolis, beginning of XVIIIth dynasty. Glas is made by melting a mixture of various inorganic substances, principally purified sand (silica), and cooling the melt under controlled conditions to prevent crystallisation. Frit is made of sand and alkali which is heated to just below melting point and then cooled. It is ground into powder and put in a crucible ( a small ceramic saucer) together with the other ingredients and melted together to make glas.
© Science Museum / Science & Society Picture Library