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I have used the vinegar/steel wool trick to ebonize oak. However, I am not sure WHY it works. If there's a chemist out there (Sheldon?) that can explain the mechanism in layman's terms please do. I'm mystifying my 8 year old son now with the trick, but he's asking about the science behind it.
Got this from googling "How does ebonizing wood work". It doesn't give much detail except to say the goo you make with the iron oxide (rust) and vinegar reacts with the tannin and turns black. Low levels of tannin will turn dark but not as dark as oak. Oak has a higher level of tannin than most woods.
Chemical Reaction
- Some woods contain a chemical that, when activated, automatically turns an ebony color. These chemicals are called tannins. Most woods do not have them in high enough concentrations to invoke ebonization, but a few woods do, such as oak and walnut. The DIY stain of iron oxide and vinegar provides a dark stain for any species of wood, but the very same technique applied to high-tannin woods creates the best results because the iron-oxide causes a chemical reaction with the natural tannins. It doesn't just saturate the grain with stain; it causes the wood to change color.
The iron in the steel is acted upon by whatever acid is made to come into contact with it. In this case Acetic acid, thus what you have created is ferrous "acetate" iron acetate. If instead you were to use sulfuric acid you would then make ferrous sulfate and so on. It is a simple and basic reaction between two chemical, hope that's basic enuogh and understandable for all :)
Ok, so it's ferrous acetate that's formed in the liquid. But why does it cause a blackening of the oak?
Prashan, the natural tannic acid in the oak is reacting with the acidulated iron in the wool though the acid is not necessary, you could as easily just use Ferrous sulfate to begin with dissolved in water to do the same or just buy powdered ferrous acetate. Iron will by nature just react with tannic acid either to produce the necessary blacks or greys of wood finishing past or present ok?
How does one perform this trick? Do you have to let the steel wool sit in the vinegar for a while, or is it immediate?Quote:
Originally Posted by Prashun Patel
I really don't have a clue...first time I have heard of this.
Bill
I recently did a couple hall tables with curly maple floating tops and ebonized WO bases.
For the steel wool part of the program:
Get some fine, high quality, steel wool. I use Liberon 0000.
Grab a chunk.
Scrub it a bit with warm water and dishwashing soap, then rinse-rinse-rinse thoroughly. If you use hardware store steel wool, you need to wash it very, very well to get rid of the oil.
Shred it up.
Stuff it into a quart mason jar.
Fill the jar with white vinegar.
Punch a few holes in the lid. No foolin' - the gas needs to escape.
Walk away for a good long while - I wait a week.
Strain through coffee filter. A few times.
If you want to speed up the process, load the steel wool and the vinegar in the jar without the lid on. Set it in a pan of water on a hot plate. Go to medium heat. Bring it to something less than a boil. You can't tell the heat level by the surface bubbles, because those are the gasses escaping, not the vinegar approaching boil. I stick my finger in to see how hot it is. I go to "eeeee-yikes" level, but not to "ho-lee-cow" level. Cap the jar with the holes in the lid.
This gives me a one-day turnaround.
Now, then..........this soup gave me a very dark grey - did not seem to me to be a true black.
If you want to try something really cool, google "Popular Woodworking Ebonizing Wood". You'll hit a July 2009 article.
This is basically what I did, but with a couple tweaks here and there. Fascinating. You are using powdered quebracho bark as a first step to increase the tannin levels. Instructions and source for the quebracho are in the article.
The quebracho is very inexpensive. Used for tanning/dyeing dead critter skins. Min qty is 2#, which is 6 lifetimes' supply. I gave away a lot of this to creekers last year, leaving me with one lifetimes' supply.
Scrap test piece:
Attachment 251211
Fairly lousy photo of one of the tables:
Attachment 251212
Is it black like that all the way through?
Jason
Iron reacts with vinegar (acetic acid) to produce as solution of Iron Acetate.Quote:
Originally Posted by Prashun Patel
The Iron Acetate reacts with the Tannic Acid in wood to produce Iron Tannate, a black dye.
Note: If there is not enough Tannic Acid in the wood, the results can be anything from gray to no reaction at all.
Some species of wood may have to be pretreated with a source of Tannic Acid. I normally use a very strong brewed tea or boiled oak bark.
The Japanese use this type of dye for wood and metal work, they call it Ohaguro.
It's one of the standard finishes that I use in my woodworking practice.
I'm a chemist and a woodworker with 40+ years of experience.
Hope this helps.
Kent, I think every woodworker at some point has ebonized wood in this fashion.It's one of those mystique's when coloring wood. Personally, I'll use a metal complex dye that is a saturated solution and apply it hot. I'll do this a couple of times in quick succession. In other words, I'll be having a couple of beers by the time you get half way through your process. And yes it penetrates deeply and is colorfast. At times I'll use extract of logwood as a mordant.
As with all aspects of finishing some will lean one way or the other as "the right way" to do this. I will tell you this: the dyed method will work on any wood not just tannin rich types. I'm a big fan the KISS method.
Great informative reply Kent!
Thank you for taking the time to post it.
Well done!
Bill