Howdy! Once I figure out how to add pictures I'll show you a couple sword fittings I blackened. The tannic acid route works great, and is cheap.
I make a strong tea in a pyrex pot. Normally you let a tea steep (that's called an "infusion") but I like to boil the tea for about 10 minutes or so before immersing my parts (that's called a "decoction", much stronger). I usually like to paper my parts then finish with a rough polish with tripoli which is a wax based abrasive, so that means lots of cleaning. I actually wash most of my parts with laundry detergent to remove oils, waxes, you name it.
After the parts are clean, I make my decoction, plop them in, and boil them for as long as I need to get them as black as I want. A half hour should do.
After they come out you'll notice the water is dark black, and the parts also are very black, with a black powder on them. The parts are VERY hot so wear gloves, and rub down with beeswax to seal. Buff with a soft lint-free cloth, and you got a nice pearly black finish.
The sword is going to a customer who will use it in medieval martial arts, and it's guaranteed to suffer some abuse. The pommel won't rust for many years as long as it's maintained (same as the blade really), and where the hilt suffers nicks and scrapes from other blades well that's a high wear zone. I offer an optional maintenance plan to cover that kind of abuse since it's expected.
Hopefully my rambling helps!
- Rusty
