Those pieces of glass are made of 2 layers and a series of segments, that are fused in a kiln.
- Very sturdy design - Extreme lightweight - Calculated geometry for support and ventilation - Extreme fast cooling - All the blanks are pre- curved
- This is 21 first century glass technology - Welcome to a new area of optical glass
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- To make a high quality lightweight mirror blank, all the glass components must come from the same piece of glass. This permit a zero tension differential in the substrat. - The center on gravity (COG) of a disk of glass, when bended, do not contribute much to it's structural strenght. When the COG is ''evacuated'', it will have less flexture because of the reduced weight. This permit to have an ultra lightweight mirror blank to very sturdy. - The sandwich mirror blank configuration have about 1/3 to 1/5 of the weight of a equivalent thichness of a solid disk. Also it have about 3.5 the surface of a classic mirror blank. This type of sandwich blanks are made from 3 to 5 mm thick glass. So less weight, more cooling surface and thinner glass contribute to faster cooling. - All the are pre-curved, this allow to have less distortion while cooling. Enjoy having not to hog hog the glass to create the curve. The mirror blanks are slump in the kiln using accurate forms made in cement-ceramic.
Glass hardness Here is a chart of the glass hardness of Lime, BVC and Borosilicate glass. Lime glass and BVC glass will grind and polish faster then Borosilicate glass.
Cooling time ratio. Here is a chart of the cooling time ratio between differents glass type and glass technology
Figure change during cooling. In the sandwich format, here is a estimate of the figure change during cooling. The graph show the amplitude of change per 1 deg C, in nanometers.