BK4 by Sumita

Obsolete Very Rare Environmentally Dangerous

BK4 by Sumita is an obsolete optical glass with a very rare melt frequency. It transmits from 0.28 to 2.00 µm with an nd of 1.50048 and a Vd of 66.0. It has excellent chemical resistance and dangerous environmental properties.

Refractive Index vs Wavelength
Refractive Index Calculator
Valid range: 0.27–2.0 µm
dn/dλ vs Wavelength
dn/dλ Calculator
Valid range: 0.27–2.0 µm
Abbe Number Calculator
Transmission vs Wavelength
Transmission Calculator
Valid wavelength range: 0.280–2.000 µm
Optical Properties
Refractive Index (nd) 1.50048
Abbe Number (Vd) 66.0
Dispersion Formula Schott
Wavelength Range 0.27 — 2.0 µm
$$n(\lambda) = \sqrt{2.22575 - 0.0106633\,\lambda^2 + 0.0093386\,\lambda^{-2} + 0.000363077\,\lambda^{-4} - 3.58782 \times 10^{-5}\,\lambda^{-6} + 1.96218 \times 10^{-6}\,\lambda^{-8}}$$
Thermal Properties
TCE -30/70°C (10-6/K) —
TCE 100/300°C (10-6/K) 6.5
Thermal Conductivity (W/mK) —
Heat Capacity (J/gK) —
$$\frac{dn}{dT} = \frac{n_0^2 - 1}{2\,n_0}\left[0 + 2(0)\,\Delta T + 3(0)\,\Delta T^2 + \frac{0 + 2(0)\,\Delta T}{\lambda - 0}\right] \Delta T = T - T_0, \quad T_0 = 20\,°\text{C}$$
Physical Properties
Density (g/cm³) 2.41
Relative Cost —
Mechanical Properties
Young's Modulus (GPa) —
Poisson's Ratio —
Knoop Hardness (kgf/mm²) —
Chemical Resistance
Climatic Resistance 1
Stain Resistance —
Acid Resistance 1
Alkali Resistance —
Phosphate Resistance —
Similar Glasses (Other Manufacturers)
Glass Manufacturer nd Vd Compare
BSC4 Hoya 1.50048 65.996466
H-K2 CDGM 1.50047 66.020774
BSC3 Hoya 1.498309 65.130542
BSL21 Ohara 1.503779 66.814545
BK3 Schott 1.498311 65.063609
PC1 Hoya 1.503779 66.88712
N-BK10 Schott 1.49782 66.95
BSL3 Ohara 1.498308 65.026785
BK10 Schott 1.497821 66.95447
PK1 Schott 1.503781 66.921827
Similar Glasses (Sumita)
Glass Manufacturer nd Vd Compare
BK3 Sumita 1.49831 65.1
BK10 Sumita 1.49782 67.0
K-BK7 Sumita 1.51633 64.1
BK7 Sumita 1.51633 64.1
BK1 Sumita 1.51009 63.4
K-PBK40(M) Sumita 1.51497 63.3
P-BK40 Sumita 1.5176 63.5
K-PBK40 Sumita 1.5176 63.5
K11 Sumita 1.50013 61.6
K-PG325(M) Sumita 1.50506 70.4
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