How to blacken brass ???

Meatballs · Dec 18, 2021

This is my first post here and I hope some of the experts here can help me.
I am looking for a method of blackening brass much like you see inside a camera and other optical equipment.
I have tried everything that I could find out there and nothing seems to work to get that deep black patina found inside a camera.
Does anyone have any idea of what or how anything was used to obtain this finish?
I am making optical parts out of brass and need to blacken them but so far nothing...nada, zippo ...
Anyone ??
cheers,

woodlandSerenade · Dec 18, 2021

I've read somewhere that 'lamp blackening' (i.e. soot) was used to make black pigments at one point in history. Might be worth looking into as long as the blackening doesn't migrate off of the parts and onto glass, mechanisms, etc.
Edit: This thread might be of use

BrianShaw · Dec 18, 2021

https://www.birchwoodcasey.com/products/brass-black-touch-up-3-fl-oz-bottle.html

jwd722 · Dec 18, 2021

Gun Blue used for bluing firearms works on brass. Despite the name it is actually black.
Birchwood Casey Super Blue is available at Dunhams and many other sporting goods stores.
Follow directions and with a little practice it works well.

AgX · Dec 18, 2021

There are various approaches to blacken brass. Also preparation of the metal is important too.

For a DIY approach I would advise as blackening means a 20% solution of CuCO3· Cu(OH)2 in Ammonia of 25%.

gone · Dec 18, 2021

Preparation is key. I'd just brush on or spray things w/ matte black acrylic paint, w/ a coat of primer first. That part is simple, taping everything off, cleaning and prepping the surface, maybe having to remove the film chamber from the camera, that's where the time will be spent.

AgX · Dec 18, 2021

But to me it seems the OP is looking for a way to chemically blacken brass.

John Koehrer · Dec 18, 2021

Brian in post #4 mentioned Brass-black which is chemical but in using it's very important the material is clean
even skin oil will have an effect on the finish.

AgX · Dec 18, 2021

Not only grease,but any surface alteration as oxidation will hamper the result. Though only for anti-reflection means the cosmetics may not be that important.

mshchem · Dec 18, 2021

I think black paint was used on brass flanges etc.

Philippe-Georges · Dec 19, 2021

Put some dark furniture beeswax on it, rub it evenly open, and then heat the brass with an open flame (gas soldering gun) till the wax turns black, then polish the whole thing and it will be dark brownish.
That's what sculptors sometimes do to dark patina their bronze sculptures, and it protects against the oxidising/discolouring by the rain as it is greasy.

Don_ih · Dec 19, 2021

"a recipe for a blackening solution:

25 parts of 10% ammonia solution;
5 parts of dry copper carbonate;
100 parts of water.
(optional additive 3% of gelatin or fish-glue)

'Agitate the brass to be blackened in the solution at about 100 degrees F. After blackening it should be rinsed off ad either dried or baked..... the time of treatment will be from 15 to 30 minutes to get a satisfactory black deposit.'"

found at https://www.practicalmachinist.com/vb/general/chemically-staining-brass-what-acid-alkali-207245/

It's what AgX said.

Nodda Duma · Dec 19, 2021

If you want a durable matte black finish like what you find inside a camera or other optical equipment, either sandblast the interior for the matte finish before blackening, or airbrush on a matte black polyurethane / epoxy based paint such as Aeroglaze Z306. Those are the techniques used in the professional world. You can use a cheap flat black enamel if you’re not doing this professionally. Look up the airbrush technique of flocking.

AgX · Dec 19, 2021

Flocking if not done well may be counterproductive by giving off loose fibres.

Paul Ozzello · Dec 19, 2021

Nodda Duma said:
If you want a durable matte black finish like what you find inside a camera or other optical equipment, either sandblast the interior for the matte finish before blackening, or airbrush on a matte black polyurethane / epoxy based paint such as Aeroglaze Z306. Those are the techniques used in the professional world. You can use a cheap flat black enamel if you’re not doing this professionally. Look up the airbrush technique of flocking.

Would you prime the metal first with an etching type primer or paint directly ?

Nodda Duma · Dec 19, 2021

fatso said:
Would you prime the metal first with an etching type primer or paint directly ?

Definitely want to clean / prep it first. For Aluminum a chem film first. For brass if you solvent wash immediately after sandblasting to remove loose contaminants and then paint before corrosion can set in you’re usually good. If you have to wait a while before coating then yeah a solvent wash and then an etching primer is a good idea.

eli griggs · Jan 3, 2022

You could use Jeweler's "Liver of Sulfur".

A gel type can be had from Michael's, Rio Grande or Amazon.

kinglang · Jun 21, 2022

I bought a bottle of Birchwood Casey Super Blue and it didn't work well.

grain elevator · Jun 21, 2022

eli griggs said:
You could use Jeweler's "Liver of Sulfur".

A gel type can be had from Michael's, Rio Grande or Amazon.

Now I wonder if polysulfide toner would do it.

AgX · Jun 21, 2022

kinglang said:
I bought a bottle of Birchwood Casey Super Blue and it didn't work well.

As to be expected, as it is intended for Iron and some ferrous-alloys, but explicitely not for non-ferrous metals and alloys.

Do not let you fool by the term "blackening". It is just about the intended effect, but not about the way to achieve this, which must be apt for the respective metal or alloy.

gone · Jun 21, 2022

I wonder if lamp black might not be the easiest way to go. Brass is a relatively soft metal. It's probably going to somewhat absorb stuff that you apply, vs having it sit only on the very top surface of something like hard steel.

The youtube video below shows how to blacken it lightening fast w/ the right chemical.

Lamp Black 4 oz vol

Lamp Black or lampblack is a soft bluish-black pigment that is very stable and unaffected by light, acids and alkalies. Our lamp black is of high purity made in modern oil furnaces and exhibits a slight bluish hue in tints.

www.naturalpigments.com

Jax Black Darkener for Brass, Bronze, Copper - 2 oz. | eBay

Find many great new & used options and get the best deals for Jax Black Darkener for Brass, Bronze, Copper - 2 oz. at the best online prices at eBay! Free shipping for many products!

www.ebay.com

grain elevator · Jun 22, 2022

momus said:
I wonder if lamp black might not be the easiest way to go. Brass is a relatively soft metal. It's probably going to somewhat absorb stuff that you apply, vs having it sit only on the very top surface of something like hard steel.

The youtube video below shows how to blacken it lightening fast w/ the right chemical.

Lamp Black 4 oz vol

Lamp Black or lampblack is a soft bluish-black pigment that is very stable and unaffected by light, acids and alkalies. Our lamp black is of high purity made in modern oil furnaces and exhibits a slight bluish hue in tints.

www.naturalpigments.com

Jax Black Darkener for Brass, Bronze, Copper - 2 oz. | eBay

Find many great new & used options and get the best deals for Jax Black Darkener for Brass, Bronze, Copper - 2 oz. at the best online prices at eBay! Free shipping for many products!

www.ebay.com

Nah hardness makes no difference, it's not porous. Lamp black without a binder will wipe right off, if it's in an exposed place.

eli griggs · Jun 22, 2022

grain elevator said:
Now I wonder if polysulfide toner would do it.

Be careful about out gassing with any chemicals you try.

eli griggs · Jun 23, 2022

grain elevator said:
Nah hardness makes no difference, it's not porous. Lamp black without a binder will wipe right off, if it's in an exposed place.

You might try 3 lb shellac as a medium for your lamp black, making an Indian Ink, or paint, but you'll need to knock back the shine from the shellac, that is, if you really want to use lamp black, otherwise, go the chemical route.

IMO

brian steinberger · Jun 23, 2022

Brass ager

How to blacken brass ???

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