[W&B] Grinding Ground Glass

[SBShohet at aol.com]

Sorry, my computer really has a hyperactive spastic disorder.

As I was saying...I can't supply photos until back in San Francisco, but 
technique is really quite simple: 

 First get some fine caborundum grits from a valve grinding shop (or a real 
auto supply jobber).   I don't remember the grades or numbers, but something 
you can barely feel as particulate between your fingers and one or two finer 
grades is sufficient. A couple of ounces of each will last a lifetime. Also, find 
a small rubber or plastic vacuum cup to hold the tool easily -- I lifted mine 
from a hook on the bathroom tile. You will also need to cut a small square of 
heavy window glass -- say 1.5" X1.5" to use as your "tool".   Finally, a 
kitchen baster is useful for washing.
 Make up a thickish slurry of the coarsest grit in water with several drops 
of dish detergent as lubricant.   I find a viscosity similar to heavy cream is 
convenient.   Rough cut your eventual Ground Glass substantially oversize -- 
perhaps 1.5" in each dimension   
 Then lay it on a nice flat board in a tray or something you steal from your 
wife's kitchen, put several drops of your slurry between your eventual G.G and 
your tool and, holding the tool with the vacuum cup, firmly rub the tool all 
over the glass in repeated circular motions. 
   Gradually the glass will be ground by the grit. Monitor the progress by 
washing off glass (hence the convenience of the tray and the baster).   At first 
the glass may not show even grinding because of slight surface 
irregularities, these will even out with patience, and is the reason for using a coarse grit 
for the first cut.   Once the first grinding is smooth, wash all the coarse 
grit off and switch to whatever final fineness you want. You will probably find 
that the edges don't finish as quickly or evenly as the center region, so 
don't worry about the last quarter inch; just cut to size when done--this is why 
you started oversize.

 Overall the whole process is very satisfying and tactilely pleasant. Does 
require a bit of patience, but once you have done a couple, it only takes 10 or 
15 minutes to make a nice glass. By the way, don't discard your tool; it, of 
course, also gets nicely ground and flat, so it can be used over and over, or 
cut up for viewfinders, etc..

Regards to all, Steve Shohet

PS: I should credit Chuck Stern, alas, no longer with us -- for the 
principles here.   Geraldine gets high marks for the vacuum cup.





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