[ATM] Pitch Substitute for very fast mirrors

[Kevin MIchael Zabbo <chaosopher23@yahoo.com>]

Pitch does have a lot of useful characteristics that I
won't get into here, but it has a flaw that I need to
point out.

Fast and large mirrors, say 13" f/3, have a deviation
from sphere that can be measured on a decent
micrometer, which is far too big a gap for pitch to
conform.  The pitch, even if soft, takes a long time
to flow.

Therefore, I have removed the pitch from my tool and
have replaced it with clear RTV silicone.  I pressed
it to a thin layer, perhaps 1 mm thick, using a
plastic shopping bag.

Plastic shopping bags don't like to conform to a
concave surface.  I wet the mirror first and then put
the plastic bag on the glass, and smoothed it out. 
The water stuck to the plastic and held the bag tight
to the surface (sag of .26") and when I pressed the
silicone lap to the bag, it stuck nicely.  When I
peeled the bag from the silicone, there were a few
wrinkles in the blobs of silicone.  These will be
advantageous to hold more zirc-ox suspension.

Silicone can also work when it's bitter cold, unlike
pitch, which likes it warm.  I will not work in bitter
cold, but I don't mind 50 degrees.  Silicone also
conforms as needed to the surface, and with pressure,
conforms better.

Pitch squares tend to break off at the edges if you go
too far in the stroke, leaving a messy scratch to
clean off.  Silicone takes a beating and doesn't seem
to wear out.

I use zirconium oxide powder suspended in water and a
little dish soap, and an 8" tool on top of a 13.2"
mirror.  I will let you all know if this works.  The
wire test will tell it all.

Kevin of Forest, Mississippi
Found that darkness I was looking for at mag 6+

I published my first novel!  You can get it here, from the publisher!  
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