Borofloat® Borosilicate

Borofloat® flat glass is highly resistant to water; neutral, acidic and saline solutions; as well as to chlorine, bromine, iodine and organic substances. Even over long periods of time and at temperatures exceeding 100°C, Borofloat® exceeds the chemical resistance of most metals and other minerals.


  • High thermal shock resistance
  • Low coefficient of thermal expansion
  • Excellent chemical resistance
  • Good surface quality resulting from being made via the float process
  • Good optical clarity and visible light transmission (better than soda-lime glass)
  • Commonly used as substitute to rolled Pyrex®, which is no longer produced
  • Can be tempered (heat strengthened) to increase thermal properties. Will not break into safety pattern like tempered soda-lime glass.

Sheet Sizes and Tolerances

Stock sizes (standard) ± 2.0 mm
1150mm x 850mm (45.3” x 33.5”) [0.7 - 21 mm]
2300mm x 1700mm (90.”5 x 66.9”) [3.3 - 15 mm]
*inquire about our full case pricing

Standard Thickness Available

Nominal Thickness (mm) Tolerance (mm)

0.7 (+/-.07) 2.75 (+/-0.2) 6.5 (+/-0.2) 15.0 (+/-0.5)
1.1 (+/-0.1) 3.3 (+/-0.2) 7.5 (+/-0.3) 16.0 (+/-0.5)
1.75 (+/-0.1) 3.8 (+/-0.2) 9.0 (+/-0.3) 19.0 (+/-0.5)
2.0 (+/-0.2) 5.0 (+/-0.2) 11.0 (+/-0.3) 21.0 (+/-0.7)
2.25 (+/-0.2) 5.5 (+/-0.2) 13.0 (+/-0.5) 25.4 (+/-1.0)

Tempered Borofloat® vs. Non-Tempered Borofloat®

¼” thick °F Normal Service °F Extreme Service °F Thermal Shock Resistance °F Max Thermal Gradient
Tempered Borofloat® 500 (260°C) 554 (290°C) 532 (278°C) 194 (90°C)
Non-Tempered Borofloat® 446 (230°C) 914 (490°C) 266 (130°C) 97 (36°C)

Normal Service: No breakage from excessive thermal shock is assumed. Extreme Limits: The glass will be very vulnerable to thermal shock.  Recommendations in this range are based on mechanical stability considerations only. Tests should be made before adopting final designs. Thermal Shock: Based on plunging sample into cold water after oven heating. Resistance of 97F means no breakage if heated to 147F and plunged into water at 50F. Tempered samples have over twice the resistance of annealed glass. Temperature Gradient: The temperature differential between two surfaces of a tube or constrained plate that will cause a tensile stress of 1000 psi on the cooler surface.

Mechanical Properties

BOROFLOAT® 33, which has a low specific weight in comparison with soda-lime glass, is particularly suited for applications in which weight limitations play a role (e.g. armored glass).

Density at 25 °C ρ 2.2 g/cm3
Young‘s Modulus at 25 °C E 64 kN/mm2
(to DIN 13316)
Knoop Hardness HK 0,1/20 480
(to ISO 9385)
Poisson's Ratio μ 0.2
(to DIN 13316)
Bending Strength δ 25 MPa
(to DIN 52292 T 1)
Impact Resistance The impact resistance of BOROFLOAT® 33 is dependent on the way it is fitted, panel size and thickness, the type of impact it is subjected to and certain other parameters not indicated here.

Thermal Properties

Its low thermal expansion, its high thermal shock resistance and its ability to withstand temperatures up to 450 °C for long periods make BOROFLOAT® 33 a good choice for applications which call for good temperature stability (e.g. internal panels in pyrolytic self-cleaning ovens and cover plates for high-power floodlights).

Coefficient of Linear Thermal Expansion
α (20 - 300 °C) 3.25 x 10-6 K-1
(to ISO 7991)

Specific Thermal Capacity
cp (20 - 100 °C) 0.83 KJ x (kg x K)-1

Specific Thermal Conductivity
λ (90 °C) 1.2 W x (m x K)-1

Maximum Operating Temperature
For short-term usage δ max (< 10 h) 500 °C
For long-term usageδmax (≥ 10 h) 450 °C


Optical Properties

  • Refractive index nd                             1.472
  • Dispersion (nF -nC)                             71.9 x 10-4

Chemical Properties

Hydrolytic Resistance  to ISO 719 / DIN 12 111  HGB 1 
  to ISO 720   HGA 1 
Acid Resistance   to ISO 1776 / DIN 12 116 
Alkali Resistance  to ISO 695 / DIN 52 322  A2 


Typical Applications:

  • Home Appliances
    (Interior oven doors, fittings in microwave appliances)
  • Environmental engineering, chemical industry
    (resistant linings, sight glasses for reaction vessels, microfluidic systems)
  • Lighting
    (protective panels for spotlights and high-power floodlights)
  • Photovoltaics
    (glass for solar collectors)
  • Precision engineering, optics
    (optical filters and coating substrates)
  • Medical technology, biotechnology
    (slides, titration plates, DNA sequencers, microfluidic systems)
  • Semiconductor engineering, electronics, sensors
    (wafers, display glass)



JNS Glass and Coatings is not limited to any specifications or spectral curves shown on our website. 
Please let us help you design the coating or select the glass that is right for your application! 
Fabrication tolerances and spectral tolerances all conform to the specifications to be agreed upon by JNS Glass and Coatings and the customer.