Re: ATM 10 inch f5.6 Polishing

[Ken Lowther <lowther@worldnet.att.net>]

Ryan Hess wrote:


> .  I was working on hot pressing yesterday (for
> several hours) with a huge no-contact area in the middle to show for it.  I
> had to cut the channels several times, but still no contact in 30% zone to
> center.  I have tried everything, including heavy weights and high temps.
> So, I just decided to start polishing.  

Stop now.  Put the lap in warm water or a warm oven.  Gently raise the
temperature of the whole thing.  Take a wet stick and press some
channels into the pitch.  Press  your mirror onto it.  Repeat as
nessecary.  You will, and must, come into full contact.  The channels
will let the pitch flow so that will happen.   I use a piece of quarter
round to do the pressing.  Nice 90 degree edge to use and is about the
right size for handling.  I may put my lap into the oven 5 or 6 times
depending on the f ratio before I get full contact this way, but it is
easy so why hurry or use another method?  

-- 
Ken Lowther
Youngstown, Ohio
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