Re: [ATM] Black Powder

[Charles Mitchard <charlesmitchard@iinet.net.au>]

Theres this 
http://www.newscientist.com/article/dn3356-mini-craters-key-to-blackest-ever-black.html
 I always thought that a stack of ultra sharp edges produced the 
blackest black, I'm sure I read that somewhere.

Richard Schwartz wrote:
> The blackest thing I know is the aperture of a large cavity that is nearly
> black inside.  In telescope making, we try to approach this level of
> blackness with powder (millions of tiny cavities) and with baffles (a few
> large cavities).   Perhaps if BOTH are used, superior blackness may be
> had.
>
> Most black coatings (I have no experience with powder) provide specular
> reflection at grazing angles, so it is important to keep the surface area
> subject to grazing incident light minimized.  I guess this means that
> baffles should have sharp edges.
>
> +++++++++++++++++++++++++++++++++++++++
>
> Date: Sun, 18 Nov 2007 16:59:42 -0800
> From: "Bob May" <rmay@nethere.com>
> One of these days I'm gonna grab all of the different kinds of
> black out there and see what really is BLACK.  I just tried some
> Rustoleum textured black and that is rather black.  I'bve got
> several other blacks including some Floquil engine black - all of
> the Floquil colors are very flat and the engine black is the dead
> black.; The thing is to measure the rreflection at a very slight
> angle of say two degrees and see how much of a light source is
> reflected to the photosensor.t.net
> Bob May
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>
>
>   

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