Blackening brass parts

[Dustin McAmera]

I recently bought a 9x12 Agfa Standard, which came with three plate holders. I have bought some film, and have made a film sheath (just one so far); I cut a piece of steel the size of my film, and folded some thin brass round it. It looks very home-made, but its serviceable other than being bright-coloured. I tried painting it, but the paint blocks the channel in the fold, so instead I have dipped the whole thing in some selenium dioxide solution they sell for blackening brass. The result is a dark grey, rather than black. It'll do fine, if the colour stays, and that's my question.

The solution I used seems to be used mostly for gun parts (so I thought I'd ask the Americans for advice ). There is an oil they recommend you rub in afterwards 'to displace moisture from the treated surface', but I don't want oily film-holders. So, has anybody used this stuff? Will the colour rub off if I don't give it the second treatment? And have I overlooked a simpler option? Thanks in advance!

[LarryD]

The stuff I used came from a gun shop You coated it then put it in your oven at 500F. It went real black and it did not go away.

[melek]

I agree with Larry. In fact, I think it's called "Brass Black" or something like that.

Micro-Tools.com used to sell this. It's pretty toxic and corrosive, so be careful when you use it.

[Julio1fer]

To "displace moisture" you could try rubbing alcohol, or isopropyl alcohol which is the chemical name. Be sure to do it in a ventilated place. I do not think that the surface will retain moisture anyway, it should be good to go if dried in an oven.

[Dustin McAmera]

Yes - 'Brass Black' is what I have. The instructions allow for either rubbing it on neat, or dipping the whole piece in a 10% dilution for a couple of minutes. I tried it neat on a scrap, and the finish was dark brown, and a bit blotchy. Dipping went well; even colour, and it looked black at first sight, but a lot of the colour was a loose precipitate that rinsed away immediately. The metal is now dark, metallic grey, after drying on a radiator; maybe I'll give the oven a go.
Thanks all!

[Julio1fer]

A radiator for a couple of hours in the Northern Hemisphere winter should be more than enough drying. I'd be more concerned about chemicals adsorbed on the surface, those might affect film later on.