　(BK7) optical glass has excellent mechanical properties and very low air bubbles and impurities, good scratch resistance. Because of its chemical stability, no special treatment grinding and polishing. Used in optoelectronics, microwave technology, and many other areas of diffractive optical elements.

H-K9L(BK7) propety		Value
optical	Refractive index	1.5168
optical	Abbe number	63.96
Mechanical propety	Density	2.51g/cm3
	Knoop hardness HK 100	610kg/mm2
	Elasticity modulus	82 x 103kN/mm2
	Poisson ratio μ	0.21
Thermal propety	Softening ponit	719°C
	Annealing point	657°C
	Strain point	624°C
	Thermal conductivity	1.1W/m.°C
	Specific heat	879J/kg.°C
	Thermal expansivity	7.1×10E-6/K
Chemical propety	Hydrolysis	2Class
	Acidproof	1Class
	Alkalineproof	2Class