Re: ATM polishing help needed

["gfbranden@earthlink.net" <gfbranden@earthlink.net>]

Hi, Old Salt Fish,

In my experience with a number of ATM students, if it seems to take forever
to polish, and there are still pits after many, many hours, then the
easiest way to eliminate those pits is to return to fine grinding with much
finer abrasives. I have found that when students try jumping from 12 or 9
micron directly to polishing, then they are unsuccessful at the polishing.
Try going back to 9 micron, then 5 micron, and make sure that all of the
larger pits are gone. Then go on to polishing.

As for pitch, I assume that roads in your part of the world are made either
with asphalt or concrete, and that flat roofs for offices and apartments
are made with pitch/tar? If you boil and strain the asphalt or roofing
pitch, and perhaps add some beeswax or turpentine or rosin (from trees,
and/or for use by violinists in improving the sound of their bows), then
you should be able to make a decent pitch lap after some trial and error.

It is also possible to glue good-quality paper to the tool and then use DRY
rouge or CeO for polishing, but people haven't done this very much in many
decades.

Polishing pads might be a good idea, if you can find them, but they don't
get rid of large holes either.

But I would strongly recommend going back to fine grinding with finer
grades, and making sure that all of the little holes are gone.

You can also use elutriation techniques to make sure that your fine
abrasives don't contain larger grit sizes. All this means is that you mix
up a slurry of the fine abrasive with water, shake it up really thoroughly,
then let it settle for a while - not long. There are tables of elutriation
times, but I think that they refer to the amount of time that the
particular grit size will settle out of a column of water that is something
like 1 meter or 1 yard tall. Thus, some experimentation will be necessary
if you are using a plastic bottle. In any case, after the slurry has sat
for perhaps 1 minute, then carefully pour off all of the liquid; the large
particles will have settled to the bottom.

I hope this helps.

Guy
-----------
Hugues.Laroche@ses-astra.com wrote:
===========
Okay I will try CeO, but pitch lump seems disappeared here,
========

If you have a spectacles maker around you might get your hands on polishing
pads. They work faster than pitch and are OK as far as polishing is
concerned. My experience is relatively good with them, except that you
can't push the wets as far as for pitch without risking sleeks/scratches,
on the other hand, the drag is more regular. For figuring though, you may
want to use pitch anyway.

At the limit I could send you a few polishing pads, but I have first to see
if I have enough still for my own use.

Good luck,

Hugues Laroche



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