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lead
CATEGORY: geology
DEFINITION: A soft, silvery-white or grayish metal that is very malleable, ductile, and dense and is a poor conductor of electricity. Known in antiquity and believed by the alchemists to be the oldest of metals, lead is highly durable and resistant to corrosion, as is indicated by the continuing use of lead water pipes installed by the ancient Romans. In antiquity, galena (from which silver may also be extracted) was the main source of lead in the Old World, although anglesite and cerussite were also exploited. Lead was used to make patterns for casting, to wet bronze and ease its casting; in making glazes; and alloyed with tin to make soft solder for joining metals and pewter for tablewares as well as for pipes roofing etc. The first evidence for lead-extraction in parts of Europe is the addition of the metal to bronze during the Late Bronze Age.
lead bronze
CATEGORY: geology
DEFINITION: An alloy of copper and tin with lead, often 60-70% copper, up to 2% nickel, up to 15% tin, and lead. The presence of lead, which remains free in the alloy as opposed to becoming part of the crystalline structure, increases the fluidity of the metal in its molten state and makes the casting of finely detailed objects easier. It is used as a bearing metal.
lead glaze
SYNONYMS OR RELATED TERMS: lead-glazed ware
CATEGORY: ceramics
DEFINITION: A type of glaze found on European pottery and the soft-fired earthenware of the Han dynasty of China. It was probably invented by the Greeks and/or Romans by the 3rd century BC, involving either dusting the unfired vessel with galena (lead ore) or dipping it into a mixture of lead ore and water. The glaze fuses in one firing. The natural color of lead glaze has a yellowish tinge; after the 13th century copper ore was often added to give a greenish-gray effect. In China it was used for vessels and miniature ceramic sculptures in funerary deposits.
lead isotope analysis
CATEGORY: technique
DEFINITION: A technique based on the relative abundance of lead isotopes, which differ according to the origin of the lead, allowing scientists to pinpoint the source of a piece of lead once the ratios of the isotopes have been determined. A mass spectrometer is used on a small sample to determine the ratio of the isotopic concentrations, which are similar in different regions if the geological time scale is similar. The method can be used to identify sources of lead impurities in other metals as well as in glass and glaze.
potash-lead glass
CATEGORY: artifact
DEFINITION: Glass based on potash as a flux with high concentrations of lead. It is heavy, lustrous, and more refractive than other forms of glass.
window lead
SYNONYMS OR RELATED TERMS: window-lead
CATEGORY: artifact
DEFINITION: Lead came subdividing the quarries of glass and holding them in place in a leaded light.

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