K9 glass, sometimes referred to as K9 crystal, is a variety of optical
borosilicate
Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Borosilicate glasses are known for having very low coefficients of thermal expansion (≈3 × 10−6 K−1 at 20 °C), ma ...
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) is the unit of measurement of an object's or substance's resistance to being deformed elastically (i.e., non-permanently) when a stress is applied to it. The elastic modulus of an object is ...
per
pascal
Pascal, Pascal's or PASCAL may refer to:
People and fictional characters
* Pascal (given name), including a list of people with the name
* Pascal (surname), including a list of people and fictional characters with the name
** Blaise Pascal, Fren ...
of 8x10
10, a
Poisson's ratio
In materials science and solid mechanics, Poisson's ratio \nu ( 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 Pois ...
of 0.21, and a density of 2510 kilograms per cubic meter (less dense than most other leaded glass).
Its high
refractive index
In optics, the refractive index (or refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.
The refractive index determines how much the path of light is bent, or ...
(for a leaded glass) and exceptional clarity 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, Austria, and has existed as a family-owned business since its founding in 1895 by Daniel Swarovski.
The company is split into three major industry areas: the Swarovski Crystal ...
. The US equivalent of K9 is
BK7.
References
Glass types
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