Ebonol C blackening problems

A. There are two basic options. Both involve making sure the brass is very clean before you start or you will have problems with adhesion and good film thickness. I suggest you give the brass a very good clean in both acid and alkaline cleaners; the exact process will depend on what you have available. You can then paint the brass with a suitable paint; probably acrylic is the best option, although if you have access to electrophoretic paint, this is better as it will get into all nooks and crannies and will give a more consistent coating.

Secondly you can dip the brass into a sulfur solution. This is usually made by dissolving flowers of sulfur in a solution of sodium sulfide. The solution will go a sort of yellow colour and will stink, but it is very good at blackening metals. However, its success may be dependent on the type of brass you are using as different brasses have different amounts of zinc in them.

To get best consistency, try carefully etching out the brass from the surface, but be careful, as removing too much zinc will result in "dezincification" which will leave a copper sponge with no structural strength.

A. Ebonol C is the world's standard for applying black oxide coatings on copper and its alloys such as brass. Nearly everyone in the finishing world has done it at one point in their career. There hasn't been any change in the formulation of the material, to my knowledge and on going experience, and while the manufacturer's name has undergone change after change due to acquisition, it's the same old Ebonol C.

Couple of thoughts: if the Ebonol hasn't changed and your process for applying it hasn't changed, look at what happens ahead of Ebonol application. Specifically, what buffing compound changes have been made. Also, what about your brass - has the lead content or other alloying elements changed? In order to get the best black on brass, sometimes need special "Brass Activator."

As one who owns a shop that has done Ebonol C for nearly 40 years and still gets out and dips his hands in the "vats", better look elsewhere. Our Ebonol is still working fine.

A. Check your acid activator.

A. I use a chlorine solution to blacken sterling silver and I also use iodine [affil links], like you buy for cuts, to blacken gold. Try one of those to blacken the brass.

A. Hi Hayden. Selenium dioxide is what trophy suppliers use to get the dark black lettering on trophies. Ebonol C is the best known commercial blackening process for brass.

Sorry, we can't print any comments about what Carl Aubock IV specifically might or might not do -- that would be a bit too close to crowd-sourcing industrial espionage :-)

Regards,

A. What Ted refers to is also the chemical bath that faucet companies use to create an oil rubbed bronze patina on brass. It results in a black finish if you don't do it right. I know this for a fact since we just went through the process of matching an oil rubbed bronze patina with a slightly brown tinge. The bath is an acidic solution containing selenium, and is commercially available.

A. There's another, completely different brass blackening process. I do not have the formula in front of me, but you'll find it in the OLD "Metal Finishing Guidebook". copper carbonate is dissolved in full strength aqua ammonia, and the parts immersed in it at room temperature. A shop I used to work for used this method on some brass cylinders they got once in awhile and it seemed to work fine.