There are many ways to ebonize wood, which is the process of turning something like oak into a pitch black stained wood using the tannins and reaction to iron oxide like in this article by Popular Woodworking.
I started making the solution. Vinegar and steel wool that I washed in soap to make sure the oil and grime is gone.
Let it sit for a week, any shorter and I don’t think the solution is strong enough.
After a week you end up with this fine looking mess
You’ll need to strain it using a coffee filter to remove any sediments. You end up with a fairly clean solution.
Then it’s a matter of rubbing the wine tannins (you can get those at any wine store) into the wood, letting it dry before you apply the iron oxide or it won’t react as well.
As you can see oak (left stick) had the most immediate reaction after one application. Maple (middle) was more blueish on the initial rub, and cherry (right) just looked washed out. But with further layers, you will get a dark finish from all 3, but there will be a color variation because of the wood’s natural reaction to the chemicals.
In the end you can have quite a nice effect like on this serving tray I made. It was finished with French polished shellac, and that really deepened the resulting black tone on the oak.
A close up of the details