Re: [ATM] Turntable and weight

["Jerry" <wa4guu@verizon.net>]

Mike
That was some ugly mirror. Is it aluminized? I don't know if that is etched.
I can think of other possible explanations. Hot pressed before figuring?
Etched is as good as any I can think of though. But I have to think of how
to explain why I don't have that problem and I take no special means to
avoid it. At least I don't think I do. 

I'm surprised sometimes looking at commercial mirrors. Some of the ugly
stuff I've seen I could not do to a mirror on purpose... or by accident for
that matter.

I've used rouge and cerium oxide on pyrex. I have used rouge, cerium oxide
and zirconium oxide on crown and flint. Not much difference except for the
sound of zirconium oxide and the mess of rouge. Having learned to contain
and limit the mess of rouge, if I had to choose only one it would be rouge. 

Mark
I have seen a lap print on one surface and as you describe, I could see it
plainly just looking at the surface. But there are special circumstances
that leave open the cause. It might well not be etching. I used a pitch lap
to support a lens while working the other side. It was in contact for a
relatively long time but it could probably move back and forth a hundredth
inch or so. So it may be that the lap worked the print in rather than
etching. Also I let it dry. I have left laps in contact with mirrors (wet
and dry) longer than the lens surface was in contact with the lap. In the
case of the "printed" lens it was with zirconium oxide. Hummmm..

Maybe it is the polishing agent or maybe it is the glass. And then I think
of Mike's Cave mirror (which is almost certainly pyrex) and I know that I
have had laps in contact with the mirror longer than Cave likely would have.
Maybe it is the water. Where was that guy from? Man! I wouldn't drink the
water there if that mirror was "lap etched." 

Looking at Mike's mirror and thinking some more I would say if it is etched
it is the facet that etches not the slurry in the channel. I can see at
least one hex shaped "facet" in the surface that is low. So it would seem
that the pitch hasn't been ruled out.

What do y'all think? Is it the facet or the slurry in the channel that
etches?

I figure using a full size lap and for local correction accented pressure.
So even for working a single zone the lap still works the entire surface.
Maybe that is why I don't have a lap print. I could be wiping it off.

Jerry


 
 





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