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And use TrueVue UltraVue glass. 2.0mm thick and blocks 98% of reflections with a coated surface. Nothing I hate more than seeing my reflection in the GG...
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 Originally Posted by steven_e007
None of them give nearly as good results as using some fine powdered grit and using a glass block as a grinding blank.
I'm curious -- why does the block have to be glass?
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I think it is believed that a glass block will be perfectly flat, leadingto a more consistent ground flass surface.
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Originally Posted by BobD
I'm curious -- why does the block have to be glass?
Because the grits grind both surfaces, if the material's softer it'll get ground in preference to the glass if harder the ground particles from it will interfere with the grits ands it can scratch the glass being ground.
When grinding plastics glass tends to cause scratches very easily, so you grind with something similar.
Ian
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Originally Posted by Ian Grant
Because the grits grind both surfaces, if the material's softer it'll get ground in preference to the glass if harder the ground particles from it will interfere with the grits ands it can scratch the glass being ground.
When grinding plastics glass tends to cause scratches very easily, so you grind with something similar.
Ian
No. If the material is softer, the abrasive will embed in it, forming a lap, grinding the harder material. It doesn't have to be a block of glass, a block of steel will work as well. One advantage of using a block of hard material is the fact that the abrasive will not embed, making it easier to attain a random pattern.
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Originally Posted by E. von Hoegh
No. If the material is softer, the abrasive will embed in it, forming a lap, grinding the harder material. It doesn't have to be a block of glass, a block of steel will work as well. One advantage of using a block of hard material is the fact that the abrasive will not embed, making it easier to attain a random pattern.
Sorry you're the one who's wrong, if you use a plastic block to grind glass or vice versa ithe grit doesn't embed in the softer plastic. Of course that changes if the material is very soft.
Ian
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I will take Ian's advice on this.
When grinding lithography stone to a certain coarse level, we always apply the grits in between two blocks of stone and move the top stone in some sort of "random" pattern. This is hand-down experience of past few hundred years for lithographic printmaking, I am not sure what is the theory behind.
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An interesting alternative to ground glass...
... from none other than Sir David Brewster, 1853:
Lay a piece of clean glass flat and level on a surface.
Pour just enough skim/1% milk on the surface of the glass to cover it completely.
Let it dry!
(spray it with matte fixative afterwards to prevent "deterioration" of your focusing surface!).
– from Primitive Photography by Alan Greene, Focal Press, 2002 ISBN 0-240-80461-9
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brilliant, honestly... what a clever idea.
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