"Wenge-ing" white oak
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Spanish
Turning oak black with an old-time method. August 29, 2001
Q.
I am looking for a method/stain to give white oak a wenge look. Any suggestions?
Forum Responses
There are always analine dyes, but I use a very old formula that I picked up somewhere along the way. I have adapted this somewhat. The original recipe called for a couple of horseshoe nails in a crock of vinegar.
Take a quart (or more) of vinegar and shred a 0000 steel wool pad in it. It will dissolve over a period of a few days to a week. Use this to wipe on the white oak and it will turn it black right before your eyes. This was taught to me as a way to "ebonize" oak. It works very well but it does raise the grain, so it needs to be lightly sanded. This light sanding will bring back some of the oak color and give the darkened wood some depth. With a little patience and some practice this can be a very beautiful finish.
Will it act the same way on red oak? Is one type of vinegar better than another? How deep will the black color penetrate? What would you use for a topcoat (over vinegar)? Would you get better results, generally, with dye?
It would be similar with red oak. The red in the oak tends to make the color more purple and less black. The mixture turns hard maple a beautiful gray color. The color only penetrates the wood slightly. Because it is so wet, the vinegar will raise the grain slightly. A light sanding will bring some of the oak color back and leave some of the black. This requires some practice but the effects are quite dramatic once done. Of course this just adds color. Once it has dried and been sanded a little, I use standard sealers and topcoats to finish it off. This is not a stain but a chemical reaction. The steel suspended in the vinegar reacts to the tannins in the wood. This creates the color change.
As for being "better" than dye it would be hard to say. Dyes are easier but the effect is different. I just thought you might enjoy learning how this was done "way back when".
The stain is called iron tannate (iron plus water plus tannic acid). It will penetrate a little if applied and wiped off. If soaked, it will eventually go through and through. You can also apply strong oxidizers (ammonia) to "age" the oak quickly.
If you apply an acid to iron tannate stain, even a weak acid like oxalic acid (see the pharmacist for some), you will instantly remove the stain. In fact, oxalic acid is used to remove iron stain from wood, sinks, toilets, bathtubs, etc. Use a weak solution.
Gene Wengert, forum technical advisor
If you cover the container used to create the dye, be sure to have it vented to let any gas that is generated escape. A friend has used this dye on local red oak to good effect.
I tried it on local pine (WY) that weathers to gray. It made an acceptable match on end grain, not exact but close enough for an outdoor bench of weathered wood. And the post about venting should be heeded. I put mine in a plastic milk jug and the jug has been expanded.
