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what is a sandwich mirror blank

Those pieces of glass are made of 2 layers and a series of segments, that are fused in a kiln.

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​- Very sturdy design
- Extreme lightweight
- Calculated geometry for         support and ventilation
- Extreme fast cooling 
​- All the blanks are pre-            curved 




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 - This is 21 first century glass          technology
 - Welcome to a new area of optical glass


 


Beware addictive product

   - 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 of 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 that are very sturdy.
   - The sandwich mirror blank configuration have about 1/4 to 1/8 of the weight of a equivalent thichness of a solid disk. Also it have about up to 4.5 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 blanks are pre-curved, this allow to have less distortion while cooling. Enjoy having not to 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. 
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Effect of gravity, in nanometers.

Cooling time ratio. 
Here is a chart of the cooling time ratio between differents glass type and glass technology
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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.
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Sandwich mirror blanks are made of soda lime glass, very lightweight and low cost . . .
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Sandwich mirror blanks are also made of BVC glass. Very lightweight and very fast cooling . . . 

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Sandwich mirror blanks will be soon made of borosilicate glass. Ultra lightweight  and very fast cooling . . . 
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  • Home
  • About Us
  • sandwich mirror spec
    • lime glass
    • BVC Glass
    • borosilicate glass
  • Dobs telescope
  • Thin pre-curved mirror blanks
  • Slump service
  • do & do not
  • Contact