On Thu, 30 Mar 1995, Chuck Grant wrote:
> > Note that to 'appear' black doen't necessarily mean it must be painted
>black.
> > For instance the reflections from the lower section of tube in (3) are
> > returned back along a 'glancing angle' and in this case a *smooth, gloss*
> > surface offers less reflection than a roughened one. Of course the smooth
>
> Excuse me, but simple experiments seem to show clearly that
> smooth gloss surface + glancing angle = really good mirror.
> This would seem to be to be a very serious mistake.
I'm not exactly sure what the original poster had in mind, but some baffle surfaces should be left glossy, though still as black as possible. It depends on where the residual light will end up. The advantage of a specular baffle is that if you know where the light is coming from, you can predict where it will go, or even better, direct it someplace harmless. A matte surface, on the other hand, scatters whatever light does reflect off it randomly. So, even though matte surfaces tend to be blacker than specular ones, it's usually best not to put them where they can "see" the mirror.
Of course, if you don't have any baffles, and you're just blackening the inside of a tube, I'd guess that you want to make that surface quite rough.
Sam Paris