Blackening brass tips please

[336v]

Hello all,

I've made a multi-exposure falling plates pinhole camera and each plate is a brass stock 0.25mm thick. It has cutotus in 4
corners for the corners photo paper to into. My question is about blackening the plates - for initial experiments I just blackened
entire surfaces (front and back) or each of 10 plates with chisel black Sharpie, but need some better method. First, Sharpie
gives quite shiny (not matte) surface, and it also is dirty - emulsion side of photo paper while plates are stacked, touches
the back of the previous plate in front of it - and the Sharpie-painted surface of the back makes dirty spots on the emulsion.

Any suggestions how to blacken brass sheet material without making black layer very thick? I have 10 exposures camera, so
10 sheets are stacked together, and any extra thickness on both sides of each brass sheet will add 20x of this thickness to the
entire stack - not good. The thinner - the better. Has anyone tried anodizing or chemical etching blackening?

Thanks!

 

[fgorga]

Haven't done this in decades, but I used Jax Black (which is available on Amazon) for blackening metal model parts.

See, for example...

The Model Boatyard - Blackening Brass

 

[reddesert]

Flat black spray paint, or Krylon Ultra Flat Black, is good for blackening surfaces. It is perhaps not ultra thin, but matte finishes usually aren't ultra thin.

 

[DWThomas]

There used to be a liquid called "Blacken-It," sold for model railroad use. Alas, the last time this topic came up it appears it is no longer made. There are apparently similar magic fluids for jewelry making use. I have heard that direct sulfide toner can do it, but personally had no luck trying to do that; maybe the pH needs to be adjusted or the brass acid etched first. My 4 oz bottle of Blacken-It will surely outlast me, as one Q-tip worth of the stuff can do a pinhole!

Paints are OK for interiors of the camera "box" but I prefer to keep that sort of stuff away from the actual pinhole. A rather teeny blob on the edge of a hole can be troublesome.

 

[reddesert]

I agree that spraying paint on a pinhole is not desirable - unless you can paint the substrate first and then make the pinhole. I understood the OP's application to be blackening film (paper) holders.

 

[Ian C]

The following YouTube video shows how to do it using Birtchwood Casey Brass Black.

Brass Black™Touch-Up

www.birchwoodcasey.com

 

[grain elevator]

Sulfides are used to blacken brass, so if you have any sepia toner around, try that.

 

[brian steinberger]

There is a product called brass ager. Works well to darken brass. Longer the brass sits in the solution the darker it gets.

 

[koraks]

I'd start with matte black spray paint and see how that goes. It's cheap, simple and probably quite effective. It can be quite durable if the surface is cleaned properly and a suitable primer is used.

 

[BrianShaw]

The JAX and Birchwood Casey products have worked exceptionally well for me in different applications with similar requirements: no buildup. Both require the part to be thoroughly cleaned before application. That model boat link presented earlier is an excellent guide on this topic. Well worth a detailed review.