Materials – Aluminosilicate

Aluminosilicate is offered for flat gauge and port gauge glasses when used in applications which exceed the temperature limits for borosilicate glasses.

BAK 50

This product is no longer available for this application however we offer an alternative product in AL01 as below.


This material is selected in preference to the barium crown aluminosilicate types primarily due to its higher viscosity values:

Thermal expansion (20-300°C)               a    =  4.7x 10-6 K
Transformation Temperature                 Tg  =  715°C
Strain Point                                                Tc  =  688°C
Softening Temperature                           Mg =  910°C
Thermal Shock (toughened)                    Δ   =  300°

In some applications it is less resistant to chemical attack and should therefore be used with mica protection when exposed to saturated steam and alkaline solutions.

Hydrolytic Resistance   (DIN ISO 719)       Class 1
Acid Resistance           (DIN 12116)            Class 2
Alkali Resistance          (DIN ISO 695)       Class 3