Re: [ATM] How dark is dark?

[Andy Saulietis <iss@pvtnetworks.net>]

More on *black*

>Vladimir Galogaza wrote:
> > What professionals are doing is what is used in Hubble. The paint they used
> > is made of many small crystals that trap most of the light by multiple
> > reflections and absorptions before the rest escapes. So by definition this
> > is matte surface. I will say that its components, individual 
> "crystals", are
> > glossy.
> > Do not ask for the price of such paint.
>
>For two interesting papers on "Deep Space Black", see:
>
>http://nscicorp.com/public/DSB%20Article%20in%20Finishing%20Forum.pdf and
>http://www.nscicorp.com/public/Deep%20Space%20Black.pdf
>
>It looks *really* black, but at what cost? :-(

Note that you can only blacken Aluminum surfaces with this process..
it was developed by Martin-Marietta and called "Martin Black". It's
not a paint or coating nor is it black. It's a proprietary aluminum etching
process which makes the surface look like steeply pointed pyramids
on a wavelength scale, photons fall in and don't come out, like the 
roach traps.
When viewed at extremely low grazing angle, the coating actually looks
like bare aluminum again, you're seeing only the tips of the pyramids.
Later, Ball Aerospace developed a similar process (Ball Black), and
probably licensed it out to the vendor in the URL.

We used this process in the light shades for the Shuttle star 
trackers, which were
also mfg by Ball Aero. Looking at a sample on a table top, it looks 
like there's a black
hole there. It's *extremely* fragile and has to be cleaned using 
non-contact methods.
Touching it makes it shiny again.

Andy Saulietis 


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