Oak + Tea + Rust + Vinegar = 'black' ?

[Brian Kincaid]

I received a shop tips DVD recently, and one of the chair builders was talking about a neat finish on Oak where he coated it in Tea ("to get the tannic acid content up") then used a solution of vinegar and rust from steel wool to make a very dark, almost black finish.

Does anyone know what this is called and how I can find out more about it?

For the record I tried several coats of tea then a coat of vinegar and I got NO color change. I'm still waiting on the steel wool to rust.

Brian

[Tom Veatch]

...For the record I tried several coats of tea then a coat of vinegar and I got NO color change. ...

The color comes from a chemical reaction between the tannic acid and the iron. You need the iron to get the color change. Don't know the purpose of the vinegar (Acetic acid to speed or intensify the reaction???).

Black stains occur anytime iron and water are left in contact with a wood containing tannic acid. Don't know specifically what woods are affected, but I do know that oak and redwood are subject to the staining, having inadvertently experienced it with those woods.

[Dewey Torres]

I carelessly sharpened chisels on by bench once using Japanese water stones and it turned my red oak apron dark purple. I also know that the fumes alone from ammonia will react with the tannons in oak (especially but in other woods as well).

[John Keeton]

If you have any post victorian oak furniture (factory built) look around the screw holes. If the piece has been exposed to moisture over the years, and most have, the area around the screw will be black. That is why brass is recommended in situations where oak and moisture will be present - bar tops, etc.

I don't know, but would think the vinegar simply breaks down the iron, and adds maybe a hydrogen or oxygen factor? Maybe some of our chemists can add to this.

[Tim Thomas]

I've been looking into this technique myself and ran across this article:
http://www.paintpro.net/Articles/PP7..._ebonizing.cfm

If you scroll down and look at the left side of the page it gives a good recipe and walkthrough of the steps to use this method. I've got some red oak that I want to try it out on.

[Brian Kincaid]

Wow thanks. That is very helpful. I'll concentrate on the 'rust' for a while

Brian

[John Schreiber]

It's called ebonizing, meaning: make the wood look like it's ebony. Here's a good description. http://www.wildlifeintarsiadesign.co...izing_wood.htm

I've tried it and its success depends on the species of wood and specifically the amount of tannins. I made some very nice little shelves out of some excess mahogany and they are black as can be.

[Brendan Guyot]

I've tried this on a few red oak pieces and it turned it very dark purple. I think some people call this "iron buff".
Here's what I did:
Soak very fine 0000 steel wool in vinegar. Use pickling vinegar, which has even higher acetic acid content (about 7%) than normal vinegar (about 5%). Let this soak for at least three days, but do not seal the container since it releases gas. Poke holes in the lid or something. I don't think rust has anything to do with this mixture; it's just the reaction between the acetic acid and the iron in the steel wool. Make sure the steel wool is the bare steel type (not waxed, which apparently exists).
After letting it sit for at least three days (5 is probably better), I just wiped it onto the red oak. Wait a few minutes, and it'll be really dark! I tried this after one, two, three, four days, etc. and the color turned from a light grey after one day to a dark purple after about 5 days.
If you want really dark black ("ebonized"), try to apply some Minwax ebony stain over top. The pigments will fill the open pores and you will get a really black finish.
Apparently this type of finish is more resistant to fading due to sunlight (light-fast) than other dyes. Not sure if there is any truth to that, but it makes sense since it is a chemical reaction, not a dye.
I haven't had any use for this type of finish yet, so I can't share any project pics, but I thought I'd offer my experience.
Brendan

[J. Larry Bailey]

I've been using this technique for several years with differing degrees of success. The higher the tannic acid content of the wood the better. The inatial application of the iron/vinegar solution does turn the wood dark blue to purple. Allow the item to dry and the wipe with a non-detergent amonia, using all appropriate safety precautions. The ammonia will turn the item black. I've used a variety of top coats an these projects and never had a failure.