How to blacken brass, advice needed.

[jgmick]

I want to make some brass parts black. I bought some commercial stuff that is supposed to do that. Tried it out, yep, it turns the brass parts really black, BUT... There is about zero durability in the coating. Rubbing it even slightly takes off nearly all of the black color. Disappointing.

Am I doing something wrong with surface prep? I tumbled the parts in a deburring tumbler, then washed them down with solvent before soaking in the solution. Do I need to do something like sandblasting them before treatment? Something else?

Are there better and lesser brands of blackening solution out there? If so, what's a good brand?

Is there an electrolytic process like anodizing for aluminum that works on brass?

Got to get something better than what I have now. Open to suggestions.