Re: ATM [long] Getting the smoothest mirror (no dog biscuit)

[mark cowan <cowanm@open.org>]

Ken Hunter wrote:

> When warm pressing...
>
> DO NOT START POLISHING UNTIL LAP AND MIRROR COOL TO UNIFORM (ROOM) TEMP.
>
> Warm pressing will heat the mirror at the lap facets and the mirror will
> be a tad bit cooler in the channels. Result: Raised bumps on the mirror..
> These bumps will give you very interesting but totally undesirable effects
> on the surface of the mirror if you try polishing when warm.

Well, I don't agree with this, Ken... 8^)

I start polishing immediately after finishing the quick, heavy warm press.
Having noticed long ago that the best polishing happens with warm laps, and
that a result of extended polishing sessions is a warm lap and mirror, it
makes sense.

But then I heat BOTH the lap and mirror to the same temp (warm water bath)
before pressing.  Heating only the lap would be a mistake, as the kind of
thing you mention could happen.

Best,

Mark Cowan
Salem, Oregon