Re: Flat black paint

Brahma wrote:
> Hello fellow pinhole camera engineers, which paint or spray-paint is the
> best and most matt for painting the inside of a camera?
>

Krylon Ultra Flat Black is used by many ATMs (Amateur Telescope
Makers). It isn't really great, but it's about the best easily
available (in the USA) commercial flat black paint. In general
painting a surface flat black isn't the best method, but it is easy to
do.

When checking a surface for "flatness" be sure to look at a glancing
(shallow) angle to the surface with a bright light source also at a
glancing angle. From face on most flat black surfaces look to be
non-reflective, but from an angle they reflect a lot of light.

There was a survey of different surface treatments used to prevent
reflections published in an astronomy magazine. Flat black paint was
worst. Black flocking paper was better. Black velvet (with the knap
in the correct direction) was next up (although expensive). The best
surface treament was something mixed with flat black paint to break up
the smoothness of the surface. Crushed walnut shells (also used for
non-slip floor surfaces) mixed in with the paint worked very well.
Sawdust was OK, but it depended on how you got the sawdust. Some
methods of generating sawdust (table saws I think) wound up polishing
the wood, thereby increasing the reflectivity. Unfortunately the best
treatment wound up being the hardest to apply.

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