Re: ATM rough polished surface

[fieldsj@coned.com (J FIELDS)]

>
>After 8 hours of polishing, I still see a uniform distribution of small
pits or bumps on the mirror surface that are not oriented in any particular
direction and that do not seem to lessen as polishing continues.  I would
hesitate to call them ripples, but in my 40x stereoscopic micrtoscope they
do look like little cusps, with high spots and indentations.  I do suspect
that the 3 micron particle size in my CeO (Rhodite 90 from Universal
Photonics) might have something to do with this situation.  Tonight I plan
to examine the surface using higher magnification to get some better
measurement of the surface defects I am trying to describe.
>
>

After careful examination at high magnification, I have to admit now that
what I was describing as a "rough surface" was in fact due to leftover pits.
At 600 power, there really is no question as the bottoms of the partially
worn-away pits show clearly as little cusps that emerge onto the surface.  I
plan to continue polishing with my Rhodite 90 cerium using thinner mix, slow
heavy pressure until I get to the bottom of the leftover pits.

By the way, further research shows that the Rhodite 90 particle size (3.4
microns average) is right in the same range as Lensmax (3.5 microns aps) and
quite a few other CeO products.  Rhodite 90 is listed as being 60 percent
CeO, 75 percent total rare earth oxides; Lensmax R is listed as being 50
percent CeO, 55 percent total rare earth oxides (Source: Universal Photonics
table on polishing compounds, p. 14).  There may be other variations in
specs between these products. 

Thanks to all who replied with helpful advice.

Jon Fields
Jon Fields