The next time you’re working on a project that calls for a dark, opaque accent, a piece that looks like ebony, try ebonizing wood for just the right look. It’s a fairly simple process, but works better on some woods than others. This story will give you what you need to know to ebonize wood in your shop.
Ebonizing wood is not the same thing as simply coloring wood with ebony stain. When you ebonize wood you’re causing a chemical reaction that makes the material turn black. The benefit to this process is opacity. When wood is stained you can sometimes see the grain through the stain. When wood is correctly ebonized it becomes pitch black, and you won’t be able to see grain through the color.
It’s important to understand that this is more art than science. You should definitely experiment before using this technique on a project.
Suitable Woods. Ebonizing depends on the wood having a lot of tannin content. As a rule hardwoods have more tannins than softwoods, and dark hardwoods more than light hardwoods. That makes oak, cherry and walnut good candidates for ebonizing. Birch and maple are not good candidates, but I’ll show you a way to work around their shortage of tannins.
Even among the usual suspects there’s tannin and there’s tannin. One piece of walnut may ebonize completely differently than another. You’ll need to experiment with the pieces you’re using to see what it takes to get the results you want.
Start by washing the steel wool with soap and water to remove any oils. If you don’t do this the oil may prevent a reaction with the vinegar. With the steel wool in a glass jar, pour vinegar over it. You’ll know it’s working when bubbles are coming off the steel wool. Bubbles should start to form within minutes of the vinegar contacting the steel wool. You can cap the jar, but cap it loosely. The gas must be allowed to escape.
The steel wool and vinegar need some time to react; a couple days would be good, a week would be better. If you suddenly realize you need iron acetate for a project NOW, you can accelerate the reaction process by heating the mix in a double boiler. Gently heat the mix for a couple hours, then let it sit overnight. You should be able to use it the next day.
In addition to making iron acetate, make yourself a nice pot of tea. Steep 10 tea bags in a quart of hot water to make a really strong brew. The tea will be used to add tannins to wood.
A good jar of iron acetate will look pretty icky.
Do Some Testing. Brush the iron acetate on to some sample boards and see what you get. Results are not instantaneous. Elapsed time on these boards is two minutes. The tannin-heavy woods-walnut, oak, cherry-are much darker than the other woods.
The tea really helps. The top board is birch with tea and iron acetate on the right, iron acetate only on the left. The bottom board is walnut, raw on the left and iron acetate only on the right. The center board is walnut with tea under the iron acetate. It’s significantly darker and more opaque then the other walnut board.
You can also brush tea on top of the iron acetate. The bottom line is that tea has a lot of tannins in it, so it’s a tannin-additive for low tannin woods.
A Few Notes.
Ebonizing only affects the surface so machining, such as routed profiles, should be done before ebonizing.
The ebonizing process may raise the grain, especially if you use tea. It’s a good idea to do a pre-ebonizing grain raise. Brush on a little water and, after the wood dries, sand off the whiskers. That should prevent you from having to sand the ebonized piece and taking the risk of sanding off the ebonizing.
The iron acetate needs to get into the wood, so don’t sand finer than 220-grit or you may prevent the liquid from soaking in and having the chance to react.
Give yourself ample opportunity to experiment with this process before using it on a project. Keep the test boards and record how you made them.
Photos By Author
Click here to watch a related Ebonizing Wood video clip.