Re: [ATM] ATM Digest, Vol 51, Issue 36

["Bob May" <rmay@nethere.com>]

Actually, pitch is an option and you only need a small bit to
keep the glass in place.    With hand grinding, it is rarely
necessary to tie the glass down iwth anything to keep it from
moving about.  With a machine, often just the loose ring around
the glass will insure that there is absolutely no movement of the
glass   The drawer bottom rubber plastic matting does an excelent
job of keeping things from moving about and it usually does a
good job of allowing the glass to keep its proper shape.
Pitch is easily taken care of by two different means.  First is
to freeze it.  Tht makes it very brittle and stops its desire to
stick to things.  An hour in the freezer often does the job bery
nicely and allows the glass to just pop of without any problems.
Use plastic tools as wedges for this job and don't stress the
glass too much.  The other means of getting the two pieces apart
and this works best ofr t more extensive gluing of the two pieces
together is to just warm hem up and pull htem apart when the
pitch gets soft.  Unless you need a clean back of the glass,
don't consider this method as it will then take a while to clean
off the pitch from the glass.  I'll note that you don't need a
clean back to do optical testing so you can then just warm
everything up again and it's back together again!  Near boiling
hot water does an excvellent job of making pitch, especially
thinned pitch flow easy.
Bob May

rmay at nethere.com
http: slash /nav.to slash bobmay
http: slash /bobmay dot astronomy.net


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