Borosilicate - A type of glass with main glass-forming constituents silica and boron oxide. Well know for having very low coefficient of thermal expansion  (~5 × 10-6 /°C at 20°C). However, there are many different borosilicate glasses made with various expansion coefficients (e.g. Pyrex and Borofloat are 32.5 while 7059 is 49). The lower the coefficient of expansion the more resistant the glass is to thermal shock.

  Corning 7740 (Pyrex) Kimble KG-33 (Kimax) Schott 8330 Duran
Strain point 510°C 513°C 510°C
Annealing Point 560°C 565°C 560°C
Softening Point 821°C 827°C 815°C
Youngs Modulus 6.4 x 103 nbsp;Kg/mm2 9.5 x 106  psi 63 x 103  N/mm2
C.T.E. 32.5 x 10-7  cm/cm/°C* 32 x 10-7  in/in/ °C* 32.5 x 10-6  cm/cm/°K-1*
Density 2.23 g/cm3 2.23 gm/cm3 2.23 g/cm3
Refractive index 1.474 @ sodium D line 1.47 @ sodium D line 1.473
Temp Limits 490°C short term 450°C short term 500°C short term
  230°C normal service 230°C normal service 230°C normal service
Thermal shock 160°C 180°C 160°C

Grayglass Float Borosilicate 33
 - Grayglass' proprietary borosilicate glass product that has great heat resistance performance, stable chemical properties, high transmission, and is available in the thickness of 2-20 mm.

Superbly Priced!

Softening Point 820°C
Co-efficient of Expansion 33.0 x 10-7  cm/cm/°C*
Density 2.23 g/cm3
Refractive index 1.474 @ sodium D line
Light Transmission 92% (thickness ≤ 4mm)
  91% (thickness ≥ 5mm)

® - Schott Technology's brand name for its flat sheet borosilicate glass. The term borofloat indicates the sheets are formed using the float glass process technology to keep the surfaces very flat and clear like window glass.

Thickness Size (In.) Thickness Size (In.)
0.7 mm 33 x 45 5.5 mm 33 X 45
1.1 mm 33 x 45 6.5 mm 33 X 45
1.75 mm 33 x 45 6.5 mm 66 X 96
2.0 mm 33 x 45 9.0 mm 33 X 45
2.25 mm 33 x 45 13.0 mm 33 X 45
2.75 mm 33 x 45 16.0 mm 33 X 45
3.3 mm 33 x 45 19.0 mm 33 X 45
5.0 mm 33 x 45 21.0 mm 33 X 45

Rolled Pyrex- discontinued Pyrex product, borosilicate with rolled ripple like surfaces. Grayglass has various thickness of rolled Pyrex in stock from 3/16”, 3/8”, 1/2", 5/8”, 1 1/8”, 1 3/8”, 1 5/8”, 1 7/8”, to 2 1/4".
For Lighting Applications, borosilicate is a material of choice for high heat and outdoor applications. It is usually needed for safety coverings over hot fixture lamps and it is especially useful for landscape and architectural lighting, where a hot lens may be subject to thermal shock from cold rain or snow.

Alkali Free Borosilicate (7059 & 1737 glass codes) - this glass was developed for thin film electronic circuits and panels which require an extremely smooth surface with special electrical properties. The surface smoothness is .5 microinch and the surface flatness is .004 inch/inch. It is a thin clear low expansion glass. The sheets are approximately 14" x 15" and are available in .016", .020", .028" and .043" thick.

Furnace Observation Blue Borosilicate - Corning's #5331 glass is a dark colbalt blue glass that is a low expansion glass for added heat resistance in furnace site glass applications. The color is specifically designed to view flame for accurate settings or readings and still protect the viewer from harmful IR and UV rays. Grayglass carries 12" square blanks that can be ground and polished to the desired size and thickness.

Infrared Reflecting Borosilicate (IRR Borosilicate) - also commonly known as a hot mirror. This is an Indium Tin Oxide coating on one surface which is transparent to the visible spectrum and reflects a portion of the infrared spectrum back at the light source. This is mostly used in the high heat environments to protect the interior components of cameras, film in projectors, colored lenses or even people from heat caused by intense light sources. The coating is also by its nature electrically conductive (approx. 50 ohms per square). This leads to other industrial uses. Grayglass stocks IRR borosilicate in 1/8", 3/16" and 1/4" thick sheets. This can also be custom coated on pattern, color or clear float glass.

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