Ebonizing oak is done with iron acetate, and you can read a more in-depth article about the process if you like. In short, we load the wood with tannins and apply a mixture of vinegar and steel wool. This turns the wood pitch black.
I am using red oak for this table. Red oak does not have as much tannins as white oak, and the board is bone dry. We need to do something to help the chemistry along in order to get the effect we’re after in such cases. In addition, the surfaces were planed with a hand plane. This leaves them glassy smooth, and that is not ideal for this process. For applying a wax finish, sure, but not so much for stain, paint or lacquer; they need something to “bite into”. For ebonizing, we need the iron acetate to penetrate as deep as possible! The deeper it penetrates, the more abuse a piece can take before the black color disappears.
Pro tip: for a deeper color using oil as finish, sand the surface with 240 grit. This enables the oil to penetrate easier into the wood, giving a darker color. A planed surface will result in a lighter color.
I made a sinfully strong brew of black tea – forest fruit, which made my fingers smell lovely for hours after the job was done… Even after thoroughly washing them. After the tea had cooled down, I used a brush and slathered the legs with tea. This does two things to the wood. One: it loads the wood with tannic acid from the black tea, and two: it raises the grain.
A light band near the joint shows that there are some glue residue left, which I removed with a card scraper. Another advantage of raising the grain – this would’ve resulted in a very ugly blotch using any kind of finish.
Raising the grain is essential before applying any finish, and water does that exceptionally well. After the first coat of tea had dried completely, the surface of the wood was pretty rough. I gave all the surfaces a light hand sanding using 240 grit Mirka Abranet. It is an expensive sand paper, but it does not clog and it last for ages! Highly recommended.
I then applied two more coats of tea with a light sanding between coats to remove any raised fibres. Time to fetch the pointy hat and a besom!
Naturally, I did not take any pictures of the process as I was wearing gloves and tried to stay away from the fumes as best as I could. But over all I am pleased with the results. The slight brown tint actually goes well with the wood on the two chairs this table will go with. The tint will be less visible as soon as I put on any oil based finish (actually, it completely vanished). For this table, I’ll go with oil based clear lacquer for the legs and water based clear lacquer for the top. I want to keep the table top as light in color as possible, and any oil would darken it too much.
The ebonizing process did not yield the pitch black color I was after, but over all I am pleased. Compared to the untreated color of the table top, the effect is dramatic.
I did one more round of tea – iron acetate – tea. When the surface dried up, a brown “soot” reappeared. I immediately rinsed off the surface with clean water and a cloth. This took care of the brown residue. The color of the wood got slightly darker, so I decided to call it a day. The finishing process should take the color to the next level anyway.