Re: ATM 10" help - TDE?

["Tyrone Steele" <atm@pivotmusic.com>]

The sharpie test was done from edge to edge each time.
I'll try the red out test. I seem to recall that from some reading
somewhere.


----- Original Message -----
From: "Ken Hunter" <kb7h@onemain.com>
To: "Tyrone Steele" <atm@pivotmusic.com>; "Richard Ozer"
<rozer@ois-online.com>; "Richard Schwartz" <richas@earthlink.net>;
<atm@shore.net>
Sent: Wednesday, September 25, 2002 11:53 PM
Subject: Re: ATM 10" help - TDE?


>
> ----- Original Message -----
> From: "Tyrone Steele" <atm@pivotmusic.com>
>
> > I have no idea what you're talking about.
> > If you mean the sharpie test, yes that was done many times.
>
> The SHARPIE test was not designed and DOES NOT tell you
> if the mirror's surface is properly ground out to the edge. It merely
> tells you that the surface is spherical (or not). There can still be
> many larger sized pits anywhere on the mirror and the sharpie test
> will pass if the glass is spherical. It's up to you to get a
> consistant
> grind over the surface then apply the SHARPIE test before deciding
> to move to the next grit size.
>
> Perhaps you were not applying the SHARPIE test correctly or were
> unclear on it's purpose.
>
> The mirror is marked on many axis with the SHARPIE marker,
> A FEW, SHORT strokes are made and then the mirror is examined
> to see where the contact between the mirror and tool occur. If the
> SHARPIE lines are evenly ground, the mirror and tool MUST be
> spherical and if the pits are uniform at the same time, move to the
> next grit.
>
> The "red out" test is described in the ATM series of books...
> You basically hold the mirror or position yourself to see the
> reflection
> of a light bulb at a grazing angle off the surface of the mirror. By
> raising
> or lowering your viewing position you can see if the reflection
> changes
> color and determine the quality of the grind.
>
> I'm not familiar with a "blind" test by that name, perhaps Richard can
> elaborate on it or maybe it was an attempt for us to do a little
> exercise
> in Internet searches?
>
> Ken Hunter
>