B 270^®

Special Properties

• High uniform transmission for visible wavelengths
• Crystal clear, super-white appearance
• High-purity glass composition
• Excellent stability against solarization effects
• Very low visible aging when exposed to sunlight
• Fire-polished glass surfaces
• Easy processing
• High alkaline content
• Thin thicknesses can be laser cut

Typical Applications

• Coating substrate
• LCD cover glass
• Protective glass for laser welding
• Touch panel solutions
• Image-forming optics
• Electronic packaging
• Chip masks
• Optical windows and filter optics
• Laboratory applications
• Laser applications with moderate requirements
  (polishing required)
• Base glass for filter coatings
• Blanks for lenses

Related glass types

• N-BK7
  (optical glass)
• BOROFLOAT^® 33
  (borosilicate glass)
• Selected float glass
  (premium quality soda-lime thin glass)

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B 270^® is a universal, economically priced crown glass with high transparency in the visible and near-infrared range. The modified soda-lime glass from SCHOTT has a colorless, crystal-clear appearance. It is very resistant to the solarization effects that typically occur when a material is continuously exposed to the sun or UV light. When other glass materials change color, B 270^® stays white and clear. B 270^® is available as fire-polished sheet glass or unpolished raw glass ingots. B 270^®, in the form of blank-drawn sheet glass, exists in a wide range of thicknesses. For sight glass applications where the quality of the surfaces and waviness are not critical, B 270^® can be used without further treatment. If optical quality is required, B270^® flat glass materials must be ground and optically polished. Due to its purity, such polished B 270^® can be used to fabricate demanding optics that require a refractive index of around 1.52, while offering lower costs than many optical glasses.

To get a quote for glass parts made of SCHOTT B 270^® crown glass with specific dimensions, please choose a thickness from the table in the specifications or click the button below.

 

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48-hour express manufacturing

 

Specifications

Transmission spectrum

Transmission curve of B270^®

UV-transmittance at 1.15 mm

UV-Transmission of B270^®

Standard Thicknesses

Thickness (mm)	Tolerance
0.80	±0.10	✔
0.90	±0.10	-
1.00	±0.10	✔
1.10	±0.10	✔
1.15	±0.15	✔
1.20	±0.15	✔
1.35	±0.15	✔
1.50	±0.15	✔
1.65	±0.15	✔
1.85	±0.15	✔
2.00	±0.15	✔
2.50	±0.20	✔
3.00	±0.20	✔
3.50	±0.20	✔
4.00	±0.20	✔
4.50	±0.20	✔
5.00	±0.20	✔
6.00	±0.30	✔
8.00	±0.30	-
10.00	±0.40	-

Optical Properties

• Abbe numbers:
  • v_e = 58.3 +/-0.6
  • v_d = 58.5

Refractive Index (20 °C)
Description	Wavelength (nm)	Refractive Index
ng	436	1.5341
nF'	480	1.5297
nF	486	1.5292
ne	546	1.5251
nd	587.5	1.5230
nD	589.3	1.5229
nC'	644	1.5207
nC	656	1.5203

Mechanical Properties

• Density: 2.55 g/cm³
• Young's modulus E: 71.5 kN/mm²
• Poisson's ratio μ: 0.219
• Torsion modulus G: 29.3 kN/mm²
• Knoop hardness HK₁₀₀: 542

Thermal Properties

• Coefficient of mean linear thermal expansion
  (static measurement):
  • 9.4 × 10^-6/K (20–300 °C)
  • 9.0 × 10^-6/K (20–200 °C)
  • 8.2 × 10^-6/K (20–100 °C)
• Viscosities:
  • Working Point (10⁴ dPa): 1033 °C
  • Softening Point (10^7.6 dPa): 724 °C
  • Annealing Point (10¹³ dPa): 541 °C
  • Strain Point (10^14.5 dPa): 511 °C
• Transformation temperature Tg: 533 °C
• Heat conductivity (W/(m x K):
  • 0.92 (24.5 °C)
  • 1.01 (89 °C)
  • 1.08 (127 °C)
  • 1.15 (167 °C)

Chemical Properties

(not valid for B270^® i-type)

• Hydrolytic resistance according to DIN ISO 719:
  • Hydrolytic Class HGB 3
  • Equivalent of alkali (Na₂O) per g of glass grains:
    170 μg/g
• Acid resistance according to DIN 12 116:
  • Acid Class 2
  • Half surface weight loss after 6 h:
    1.4 mg/dm²
• Alkali resistance according to DIN ISO 695:
  • Alkali Class A2
  • Surface weight loss after 3 h:
    140 mg/dm²

Electrical Properties

• Dielectric constant ε_r: 7.0 (1 MHz)
• Dielectric loss tangent (tan δ): 30 × 10^-4 (1 MHz)
• Specific DC-Volume Resistivity ρ_D (Ω × cm):
  • 10⁹ (250 °C)
  • 1.6 × 10⁷ (350 °C)
  • 2.0 × 10⁶ (400 °C)
• Temperature Tk 100: 301 °C
  (for volume resistivity of 10⁸ Ω × cm)

Other specialty glass materials from SCHOTT in our extensive delivery program are N-BK7, BOROFLOAT^®, AF 32^® eco, AS 87 eco, D263 T, and MEMpax^®. For further details, please feel free to send an information inquiry.

 

All data and specifications given are average guide values and are not guaranteed. Moreover, please consider the “Notes on Specifications”.

© 1994 – 2025 Präzisions Glas & Optik GmbH

Last update: June 27, 2025