The common type of borosilicate glass used for laboratory glassware has a very low thermal expansion thermal expansion coefficient (3.3 x 10−6/K),about one-third that of ordinary soda-lime glass. This reduces material stresses caused by temperature gradients which makes borosilicate a more suitable type of glass for certain applications (see below).Fused quartzware Fused quartzware is even better in this respect (having a fifteen times lower thermal expansion than soda-lime glass), however the difficulty of working with fused quartz makes quartzware much more expensive; borosilicate glass is a low-cost compromise. While more resistant to thermal shock thermal shock than other types of glass, borosilicate glass can still crack or shatter when subjected to rapid or uneven temperature variations. When broken, borosilicate glass tends to crack into large pieces rather than shattering (it will snap rather than splinter)


Mean coefficient of linear expansion a20/300 acc. to DIN 52328 3.3 x10-6 K-1
Transformation temperature Tg 525oC
Temperature fixed points at viscosity             h in dPa .s:
               1013             annealing point 560 oC
                           107.6 softening point 825 oC
                           104 working point 1260oC
Maximum short-time working temperature 500 oC
Density r 2.23 g /cm-3
Modulus of elasticity E, Young's modulus 64 x103 N /mm-2
Poisson's ratio m 0.20
Thermal conductivity lw             at 90 oC 1.2 W m-1 K-1
Temperature for the specific electrical resistance             of 108 W? cm tk 100 250 oC
Logarithm of the electric volume resistance             (W ?cm)
      at 250 OC 8
      at 350 OC 6.5
Dielectric properties (1MHz, 25 oC)
Dielectric figure e 4,6
Dielectric loss factor tan             d 37 x10-4
Refractive index nd (l             = 587.6 nm) 1.473
Stress-optical constant (DIN 52314) K 4.0 x10-6 mm2 xN-1