RE: ATM [long] Getting the smoothest mirror (no dog biscuit)

[Ken Hunter <kb7h@cei.net>]

At 11:12 AM 9/23/98 -0400, you wrote:
>
>Hi All
>
>I have read thru this tread and have come to the conclusion that I have
>some problems. I am polishing my 1st mirror, a 6" f9. I am having
>problems keeping the grooves open, I feel this has to do with the
>softness of the lap and I am working in my garage with is about 90
>degrees now.
>
>

Hi Chris,

You might want to look in the archives for some of my comments on pitch 
laps and closing channels... a lot of good info there.

I would say that your lap is TOO SOFT if you have to re-channel during
the polishing process. Trimming a bit every couple hours is normal but
if the channels are closing up... it's too soft.

You can try something before you re-make the lap.

Let the channels close up (they won't completely) and then use a piece of
cheese-cloth between the tool and mirror to make micro-channels. Warm the
lap and mirror in warm water, lay on a piece of clean cheese-cloth, squirt
some polishing compound on and lay the tool on top. Let this sit overnight
without a lot of weight. Tomorrow you can remove the cheese-cloth and use 
the lap straight-away with all those wonderful new channels and since the
main channels are already mostly closed your lap will behave as if it were
made of harder pitch.

Give it a try and let us know how it works.

Ken Hunter