[ATM] 96% Silica

[mdholm at telerama.com (mdholm@telerama.com)]

One slight worry is that not all silica is completely solid.  I think I recall
that some grades are porous.  I suspect that if you got a decent polish on part
of the blank, and then shined a strong light into it, if it were porous, it
would look milky, not clear.  Porous silica might not take a good enough polish.

Except for that, I would say grind more, worry less.  High silica content
probably means it will be harder, so you might want to use SiC farther down the
grit size ladder before switching to Al2O3.  Then when you are polishing, more
agressive polishing techniques might be of considerable help in shortening the
time.  Pads instead of pitch till you get rid of the pits, definitely CeO
instead of rouge.  Might pay to call up Salem Distributing and ask what they
recommend for polishing silica.  Maybe one of their more specialized grades of
polishing compound would speed things up.  Just make sure they don't think you
are asking about silicon.  There is a big business in polishing the element
these days instead of it's oxides.

10 or 12 by 1 inch is on the moderately thin side.  You will want to use thin
mirror techniques during grinding and polishing to prevent astigmatism.

BTW, where are you getting these blanks?

Mark Holm
mdholm@telerama.com

Mark Holm
mdholm@telerama.com