Re: ATM Melting pitch

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

There's many ways to skin that cat and each of us has a personal preference.
I consider that doing things like using a soldering iron to cut a groove to
be a bit tedious to do.  In that same vein is the cutting of the pitch and
pitching it to the base to also be a long process.
The truth is that any process that makes a bunch of grooves or edges into
the pitch will do an excellent job of preparing the lap
I prefer the use of a mold (the plastic stuff is fine) to do the grooves and
also like using some finer pitched material (the wedding veil stuff does
well as does an onion bag sized netting) when doing a warm press to roughen
up the surface of the lap.  Don't bother to get the grooves exactly some
distance apart as that is just getting picky about something that doesn't
need to be accurate.  I'll also do grooves with some strait piece of wood,
plastic or metal ala the Dobson method of just pressing it into the hot lap
and pressing the mirror on top to even the surface out.  Pits from bubbles
and so forth are also acceptable as long as they don't occupy a large area.
The thing to remember is that you're going to be working with this lap for a
fair number of hours and something that may not look very nice at the
beginning will eventually smooth out and become an excellent lap as the
pitch flows during the whole process of polishing out a mirror.  I don't
even worry about the edge shape of the lap so long as it isn't larger than
the glass and is fully in contact with the glass when you work the mirror.
A lap that is only 80% of the glass because the pitch didn't flow out that
far will work just as well as a larger lap and will assist in keeping the
dreaded TDE down also.
In other words, worry less and get started polishing!
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net