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Information on materials used
FINENESS
In the carat system, the quality – or fineness – of precious metals is expressed in carat (karat is the preferred spelling in the USA). The European system, based on one thousand weight units, is also commonplace. The two systems correlate as follows: 18-carat gold is equivalent to 750/000 gold, 21-carat gold is equivalent to 875/000 gold, platinum is equivalent to 950/000 platinum and silver is equivalent to 925/000 silver.
There is a simple technical reason for the absence of pure gold, pure platinum or pure silver in horology: both metals are too “soft” for the production of watch and movement components. Gold and platinum are alloyed with other metals to significantly increase their hardness. The different hues of pink, white and honey gold are also achieved by alloying.
BEARING JEWELS
The reference to “Rubine” on the plates of Lange movements applies to friction-reducing, wear-resistant functional jewels consisting of synthetically produced ruby for bearings, switching and detent elements and the escapement. Because of the greater homogeneity of the crystalline structure as opposed to natural ruby with otherwise virtually identical physical and chemical properties, the use of synthetic ruby is very commonplace in watchmaking today. The English equivalent of the German term “Rubine” is jewels.
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