Black lacquer. I've used RustOleum flat black with success, over 20 years ago and everything is just fine. If the edges aren't exposed to light within the lens, it doesn't matter if the paint is flat, semi flat, or gloss. If the cemented pair mounts in a metal cell, there will not be room for any but the very thinnest coat of blacking. It doesn't matter how durable whatever you use is, as it will not see any wear except for reassembly. Quite a few old lenses wre just smoked black.
Originally Posted by Tom1956
Edit - I forgot to mention that you can make a black lacquer with shellac and lampblack.
Last edited by E. von Hoegh; 08-19-2013 at 10:15 AM. Click to view previous post history.