Re: [ATM] Red Out test

["Bob May" <rmay@nethere.com>]

Basically the test is a reflection test of a bright light at a
grazing incidence and the angle of the mirror surface changed to
the point where the light "reds out".  I've got a simple drawing
of the test  on my website in the mirrormaking article.  I've
used everything from an incadescent bulb at thirty feet to a sun
reflection off a windshield at fifty feet for the light sourc4e.
The test is don e across the width of the mirror at the radial
line. Don't bother to go closer or further from that line as the
color changes and the results become "false"
Start the test by getting a reflection in the middle of the
mirror.  Change the height and angle of the mirror surface until
you get the light source to redden.  For firsttimmers, it is
often better to put the mirror on a table and jack up one point
orthe other until you get the desired results.  When you get the
red light you then can sweep the light image across the mirror
and see what the results of the color change is according to the
radial position in the reflection.  If youur surface is well
ground evenly, the red should stay the same shade.  Often what
happens is that thecolor brightens out to about the seventy
percent area or so and then darkens to a deeper red at the edge.
What is happening in the reflection is that the ligth is
interfering with itself and the longest wavelengths are the least
nulled out and thus the reflection of the light tends to strongly
favor the red.
Note that steep surfacces can make this test difficult to do.
Bob May
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