flint glass

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A soft, fusible, lustrous, brilliant lead-oxide optical glass with high refraction and low dispersion. Also called lead glass.

Century Dictionary and Cyclopedia

1. n. A variety of glass in which the silica is combined with oxid of lead in greater or less quantity. The larger the amount of lead the higher the specific gravity and the refractive power, and the greater the brilliancy of the product. Flint-glass is often called crystal glass, or simply crystal, while some limit the name flint-glass to the variety specially made for optical purposes. Besides the oxid of lead, potash is an essential ingredient of flint-glass or crystal. Analyses of different kinds of crystal show the presence of from 28 to 37 per cent. of oxid of lead, 14 to 17 of potash, and 52 to 59 of silica. The flint-glass of Guinand, used for optical purposes and generally admitted to be of unrivalled excellence, contains about 43 per cent. of oxid of lead and 12 of potash. The brilliancy of crystal glass fits it for use for ornamental purposes, and especially for the most showy and expensive table-ware. The characteristic luster and sparkle due to the high refractive power of the material is brought out by cutting and polishing, exactly as is done in the case of gems. Owing, however, to its softness, crystal glass is easily scratched by careless handling and dulled by wear. The name flint-glass originated in the fact that the silica flrst used in England for the manufacture of this article was derived from flints. An essential requisite for good flint-glass is purity of the materials employed, and the forms of the furnace and of the melting-pots are peculiar. Great technical skill is required for the production of the best kind of glass for optical purposes. See glass, strass, and lens.

Wiktionary

1. n. A soft, heavy, brilliant glass, consisting essentially of a silicate of lead and potassium. It is used for tableware and in optical instruments.

GNU Webster's 1913

1. n. See in the Vocabulary.
2. (Chem.) A soft, heavy, brilliant glass, consisting essentially of a silicate of lead and potassium. It is used for tableware, and for optical instruments, as prisms, its density giving a high degree of dispersive power; -- so called, because formerly the silica was obtained from pulverized flints. Called also crystal glass. Cf. glass.

WordNet 3.0

1. n. optical glass of high dispersion and high refractive index