[...]... understanding of glass compositions, that is before the middle of the seventeenth century (see also Brill, 1962) In this book, for convenience, the term glass will be used to mean both ancient and historic silicate glasses Understanding the special chemical structure and unique physical properties of silicate glasses is essential in order to appreciate both the processes of manufacture of glass objects and. .. 2 Conservation and Restoration of Glass lightning striking a mass of sand The irregular tubes of fused silica (fulgurites) may be of considerable length Lechatelierite has also been discovered in association with meteorite craters, for example at Winslow, Arizona Tektites are small rounded pieces of glass, of meteoric origin, found just below the surface of the ground in many parts of the world, and. .. vitreous structure to describe glass that has weathered with loss of alkali metal ions, of other constituents of the glass and probably a gain in water content This ambiguous use of the term should be avoided (Newton and Werner, 1974) Network formers The principal network former in ancient glasses is silica (SiO2) Silicon and oxygen in 4 Conservation and Restoration of Glass crystalline silica (quartz)... pieces of glass, having different dispersions If the composition of the glass is known, the index of dispersion can be calculated Thus it tends to be correlated with the RI, and a cut lead crystal drinking glass is attractive because it has both high refraction and high dispersion A knowledge of the RI may be relevant in the conservation of transparent glasses When joining two pieces of glass the RI of. .. birthplace of glass at a time prior to 2500 BC Comparatively few glass objects have been excavated there, but this may well be due to the relative humidity of the soil, and to the rise of the water-table in historic times, causing the destruction of much of the early glass which was inherently unstable in its chemical composition (and therefore relatively 18 Conservation and Restoration of Glass water-soluble)... discussions regarding display and storage conditions, and the choice of materials for display, and packaging for storage and transport The prevention of further damage and decay by passive conservation, represents the minimum type of treatment, and normally follows examination and recording Reasons for not undertaking further conservation might be lack of finance, facilities, lack of an appropriate treatment... broken or cut glass surface can reflect light in the colours of the spectrum Certain types of glass are especially appealing, particularly lead crystal glass by virtue of its weight, its great clarity, its ring when lightly struck, and when cut, the sparkle and colours which arise as a result of its high refractive index and dispersion In consequence of the supposed magical properties of glass and the technological... Introduction The conservation of glass, as of all artefacts, falls into two main categories: passive conservation, the control of the surrounding environment to prevent further deterioration; and active conservation, the treatment of artefacts to stabilize them A storage or display environment will consist of one of the following: (i) natural climatic conditions (especially painted glass windows and glass mosaics... Only a few sandwich bowls have been found, and although distributed over a wide area, from the north Caucasus, central Anatolia and Italy, 22 Conservation and Restoration of Glass Figure 2.4 A bowl of sandwich gold glass Canosa, Apulia, Italy Found in a tomb with seven other vessels Circa 275–200 BC it is generally accepted that they were made in Alexandria The technique of producing mosaic glass was... perfected in Alexandria, the cultural and industrial centre of Hellenistic civilization, founded by Alexander the Great in 332 BC Despite the considerable information about Alexandria as a glass centre, only a small amount of glass has been found there The scarcity of glass in places where glass must have been abundant seems to be due to the fact that broken glass was often collected and re-melted as . Eastop) Conservation and Exhibitions (Stolow) Conservation and Restoration of Ceramics (Buys, Oakley) Conservation and Restoration of Works of Art and Antiquities. Deterioration of glass 169 5 Materials used for glass restoration 199 6 Examination of glass, recording and documentation 227 7 Conservation and restoration of glass