Re: ATM What does a "super polished" surface look like?

["Bill T." <twentiethwave@hotmail.com>]

Ed Stevens wrote:
> I took the mirror making class with Carl
> Zambuto at the Bellingham Optics Conference.
> Great class and I learned a lot from Carl.
> One thing he mintioned was that some
> manufacturers are able to "super polish" a
> mirror's surface.  I don't know what this
> means or how to tell if my surface is in fact
> completely smooth.

Probably the best an ATM can do is simply make sure his polish is truly
complete, and avoid ripply surfaces.  Ripple is the common surface disease
of otherwise adequately polished mirrors, such that "superness of polish" is
a distant concern.

What I try for is "super smooth."  Surface brightness can only shine through
when ALL the light gets bounced in the right direction.  I try to design a
figuring strategy so that I can end up figuring with an extended spell of
broad strokes to smooth out ripple.  For final figuring I usually use a
medium sized lap (about 50%+) with rounded facet edges, and very dilute
cerium oxide.  I keep the weight on the lap as constant as possible,  just
enough to maintain good contact.  I might sometimes nudge the mirror edge
with a brief touch of full sized lap.  Basically I slightly over correct the
mirror, and then bring it back with broad polishing-like strokes*.  These
techniques must also serve excellence of polish as well as smoothness.  When
I'm lucky I hit the figure and the Ronchi bands and Foucault ghost are
slippery smooth.  But when Mirror Tiki is displeased, I get a very smooth
turned edge and a very smooth big spherical zone just inside of that.

Bill T.

*others I know claim to be able to apply broad "neutral strokes" for
extended periods of time that only polish and do not effect the figure.  If
you know this magic, please contact me.