K9 glass, sometimes referred to as K9 crystal, is a variety of optical
borosilicate
Borosilicate glass is a type of glass with silicon dioxide, silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficient of thermal expansion, coefficients of thermal expansion ( ...
crown glass. The letter "K" is a reference to the German word for "crown" (''Krone'') and the number 9 refers to the lead oxide content of the glass (9%). K9 glass has high optical clarity, and is used in many contexts requiring this characteristic. It has been regarded as a difficult-to-cut material because of its superior mechanical properties. It has an
elastic modulus
An elastic modulus (also known as modulus of elasticity (MOE)) is a quantity that describes an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it.
Definition
The elastic modu ...
per
pascal of 8x10
10, a
Poisson's ratio
In materials science and solid mechanics, Poisson's ratio (symbol: ( nu)) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading. The value ...
of 0.21, and a density of 2510 kilograms per cubic meter (less dense than most other leaded glass).
Its
refractive index
In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...
is 1.517 at 590 nm wavelength
(compared to 1.523 for crown glass (soda-lime) and 1.618 for 45% leaded glass) Its clarity (90% transmission at 590 nm
[), combined with low cost have made it desirable for chandeliers, lasers, telescopes, etc.
K9 is produced in large quantities by China, which sells it at a price far below higher-quality well-known glass manufacturers such as ]Swarovski
Swarovski (, ) is an Austrian producer of glass based in Wattens, Tyrol. It was founded in 1895 by Daniel Swarovski.
The company is split into three major industry areas: the Swarovski Crystal Business, which primarily produces crystal glas ...
. A similar product to K9 (but without lead) is BK7.
References
Glass types
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