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PASTE (O. Fr. paste, See also: term is applied to substances used for various purposes, as e.g. in See also: cookery, a mixture of See also: flour and See also: water with See also: lard, butter or suet, for making pies and pastry, or of flour and water boiled, to which See also: starch or other ingredients to prevent souring are added, forming an adhesive for the affixing of See also: wall-paper, See also: bill-posting and other purposes
.
In technical language, the term is also applied to the prepared See also: clay which forms the See also: body in the manufacture of pottery and See also: porcelain (see CERAMICS) and to- the specially prepared See also: glass, known also as " strass," from which imitation gems are manufactured
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This latter must be the purest, most transparent and most highly refractive glass that can be prepared
.
These qualities are comprised in the highest degree in a See also: flint glass of unusual See also: density from the large percentage of See also: lead it contains
.
Among various mixtures regarded as suitable for strass the following is an example: powdered See also: quartz 300 parts, red lead 470, potash (purified by See also: alcohol) 163, borax 22, and See also: white arsenic x
See also: part by See also: weight
.
See also: Special precautions are taken in the melting
.
The finished colourless glass is used for imitation diamonds; and when employed to imitate coloured precious stones the strass is melted up with various metallic oxides
.
Imitation gems are easily distinguished from real stones by their inferior hardness and by chemical tests; they may generally be detected by the comparatively warm sensation they communicate to the See also: tongue
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