Re: ATM polishing question

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

I've used CeO from all concetrations of a mud to a thin slurry (1 part CeO
and 20 parts water) and have found something around 1:4 or so to be my best.
The thing here is that when you're working the mirror on the pitch )or the
pads for that matter) you do want to have enough on to be seen but not
enough CeO to where you can't see the mirror surface as you move the mirror
about.
If the mirror works very hard (you can't move it very fast even with as much
force as you can get up) then apply more CeO and when it almost floats
across the lap then you have too much CeO.
My method of making laps is pretty simple.  Warm the pitch so that you can
make a big ball of it without it sticking to your hands and as warm as
possible without the sticking.  Plop the ball (for a 6" mirror, a ball about
50mm will be more than enough) on the tool which is warm and spread it out.
Once you get the pitch on the tool out to about the 80% diameter, apply some
liquid detergent to the mirror and press on the pitch until it's close to
the edge.  Warm the surface again (I throw it in the microwave with some
water on top to warm the surface) and then use a straight edge and form the
blocks or use a mold of some kind (the garden edging material which is a
molded grating works well) to form the blocks and press the surface again
with the mirror.  Using some CeO in a thin mix will also help with the mold
release here.  It usually takes me a half hour to make a lap when I go down
to the microwave with additional time waiting for the lap to cool down with
putting in cold water usually helping in the initial cooling (you do want to
insure that the lap is in good contact with the mirror).
I might note that considering where you are, your questions, while maybe on
the more simple side of things, aren't bothersome as somebody needs to
explain some of the more basic things and thus get them in the archives so
others don't have to ask such types of questions.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net