Schott high quality borosilicate glass BF33

Introduction to Schott


Borofloatbf33 is high-quality borosilicate glass with excellent properties and a wide range of uses.

It is manufactured by Schotjena Glass Company using a micro-float process and technology. The borosilicate glass produced by this technique is homogeneous and has an excellent mirror-like surface, extremely high surface smoothness, and good optical properties.


Basic properties of Borofloatbf33 high-quality borosilicate glass

Excellent light transmittance, very low fluorescence intensity, and very high ultraviolet and infrared transmittance;

Very low coefficient of expansion, strong thermal shock resistance, and long-term working temperature as high as 450 °C;

Excellent chemical stability to water, strong acid, strong alkali, and organic material corrosion has a high tolerance;

Excellent scratch resistance, high hardness, and density can be lower than ordinary soda-lime glass by 20% ;

The extremely low alkali content can be used as an excellent electrical insulator.

Basic parameters of Borofloatbf33 high-quality borosilicate glass



expansion coefficient

(ISO 7991)

transmittance 91%
softening point


Short-term use


Long-term use


refractive index


Knoop hardness



Thermal properties of Borofloatbf33 high-quality borosilicate glass

Coefficient of linear expansion


α(20 – 300 °C) 3.25 x 10-6K-1(ISO 7991) Remarks
Thermal capacity


Cp (20 – 100°C) 0.83 KJ x (kg x K)-1 This operating temperature is only applicable if the following RTG and RTS values are satisfied simultaneously.。
Heat conductivity coefficient


λ(90°C) 1.2 W x (m x K)-1
Operating temperature (long term)


δmax (< 10 h) 550°C
Operating temperature (short term)


δmax (≥ 10 h) 450°C


The low Coefficient of thermal expansion, high thermal shock resistance, and ability to withstand high temperatures of 450 ° C over long periods make Borofloatbf33 particularly suitable for applications requiring good temperature stability (for example, the inner plate of a pyrolytic self-cleaning oven, the outer cover of high-power stage light and a high-power floodlight).

The temperature difference of the same piece (the ability of a piece of glass to withstand the difference in temperature between the heating center and the cooler edge)


The test method: heat the center of the glass plate with an area of 25 × 25CM2 to a specific temperature and keep the edge of the glass plate at an average temperature. The breakage rate due to thermal stress should not be more than 5%. Before testing, the glass plates were ground with SIC 40 type abrasive paper to simulate the extreme surface wear that may occur in service.

RTG 1 – 100hour 90 K
> 100hour 80 K

Resistance to thermal shock (the ability of glass to withstand sudden temperature cooling)


Test method: the glass plate with an area of about 20 × 20 CM2 is heated in a heating furnace and then cooled by pouring 50 ml cold water (room temperature) over the center. The rate of glass rupture should be no more than 5%. The glass plate was ground with SIC 220 type abrasive paper before the test to simulate the surface condition after actual use.

Thickness of the glass ≤ 3.8 mm 175 K
5.0 – 5.5 mm 160 K
6.5 – 15.0 mm 150 K
> 15.0 mm 125 K

The viscosity of Borofloatbf33


Working Point


104dPas 1270 °C
Softening Point


107.6dPas 820 °C
Annealing point


1013dPas 560 °C
Strain Point


1014.5dPas 518 °C
Transition temperature


525 °C

Optical properties of Borofloatbf33 high-quality borosilicate glass


Borofloat BF33 is a clear and transparent colorless glass. The excellent transmittance in the ultraviolet and visible near-infrared range makes Borofloatbf33 an ideal material for various floodlights, high-power spotlights, and sunbeds (operating at temperatures up to 450 °C). Borofloatbf33 glass has low intrinsic fluorescence and good surface quality, which can be widely used in optics, photonics, photonics, and analysis equipment.

Wave length λ(nm) 435.8 479.9 546.1
Refractive index


1.48015 1.47676 1.47311
Wave length λ(nm) 589.3 643.8 656.3
Refractive index


1.47133 1.46953 1.46916
Abbe constant


Ve=(ne-1)/(nF’-nC’) 65.41
Refractive index


nd(λ587.6 nm) 1.47140


nF-nC 71.4×10-4
Stress optical coefficient


K 4.0×10-6mm2N-1MPa-1

Fluorescence properties of Borofloatbf33 high-quality borosilicate glass


Some materials have the property of releasing electromagnetic radiation after being excited by high-frequency short waves. This property is called fluorescence. It is affected by the material’s purity and structure and depends on the energy, frequency, and excitation wavelength of the single pulse.


Borofloatbf33 is a highly transparent glass, which exhibits weak fluorescence in the wavelength range of visible light.


Select standard laser and wavelength

Wave length(nm) Lasing medium


Wave length(nm) Lasing medium


Wave length(nm) Lasing medium


308 XeCI 488 Ar 1047 Nd:YLF
325 HeCd 514.5 Ar 1053 Nd:YLF
337 N2 532 Nd:YAG 1064 Nd:YAG
350 XeF 632.8 HeNe 1153 HeNe
351.1 Ar 694.3 Ruby 1319 Nd:YAG
363.8 Ar 730-780 Alexandrite 1730 Er:YLF
427 N2 850 Er:YLF 2060 Ho:YLF
441.6 HeCd 905 GaAs 10640 CO2

Electrical characteristics of BOROFLOATBF33 high-quality borosilicate glass


Because of its low alkali content, Borofloatbf33 can be used as a high insulator, so it is suitable for high-temperature applications (up to 450 °C) where suitable non-conducting materials are needed. Because of the unique structure of borosilicate glass, Borofloatbf33 has neutron absorption

Dielectric constant


εr (25℃,1 MHz) 4.6
The leakage constant


tan δ (25℃,1 MHz) 37 x 10-4
Logarithm of resistivity lg ρ 250℃ 8.0 Ω x cm
350℃ 6.5 Ω x cm

The borofloat BF33 is available in models.



Schott borosilicate glass, non-standard, fixed thickness, custom dimensions required.

Thickness mm Tolerance


Thickness mm Tolerance


Thickness mm Tolerance


Thickness mm Tolerance


厚度mm 公差
0.70 ±0.05 2.75 ±0.10 6.50 ±0.20 13.00 ±0.30 20.00 ±0.70
1.10 ±0.05 3.30 ±0.20 7.50 ±0.30 15.00 ±0.50 21.00 ±0.70
1.75 ±0.05 3.80 ±0.20 8.00 ±0.30 16.00 ±0.50 25.40 ±1.00
2.00 ±0.05 5.00 ±0.20 9.00 ±0.30 18.00 ±0.50
2.25 ±0.10 5.50 ±0.20 11.00 ±0.30 19.00 ±0.50

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