Steel Wool and Vinegar Wood Aging/Ebonizing/Weathering (A Controlled Experiment)

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Introduction: Steel Wool and Vinegar Wood Aging/Ebonizing/Weathering (A Controlled Experiment)

I have read a lot about using Steel Wool and Vinegar to age/weather new wood. I guess the acidic solution reacts with the Tannins in the wood to create a chemical reaction to weather and essentially stain the wood with somewhat of an acid wash. I decided to do a test of various commonly found woods to see what type of coloration and saturation I could come up with.

BY THE WAY, I DID THIS ALL AT THE TECHSHOP!!!!!

I Started with a test board with a bunch of different woods.

From Left to Right, BEFORE ANY VINEGAR WASHING....

RED OAK
PINE TRIM
ALDER
CABINET PLYWOOD (BIRCH)
POPLAR
PINE
2x2 DOUGLAS FIR STUD

You can see that there are two rows of test area that has been treated with Black Tea. Many woods have high tannin concentration, but there are some like PINE that are low. Adding a tea mixture provides some tannin to aid in the reaction. This will give us an idea of what type of depth of color we can achieve.


Step 1: Different Vinegar Mixes

I decided to test just two Vinegar choices, Balsamic Vinegar and Apple Cider Vinegar. White Vinegar is also a choice, but knowing that I want a darker stain for the furniture that I will be using this on, I went with what I had heard would make a darker tint.

I chose Mason Jars from Target that were 16 oz each. I am sure that I could go much bigger, but this was the trial. I will adjust mixture if necessary.

The first Jar you see is Apple Cider Mix, with ONE WHOLE steel wool (0000), ripped into pieces to try and speed up the process of degradation. 

The Second mix is Balsamic Vinegar with ONE WHOLE steel wool (0000), ((I also did a jar with half of a steel wool, to see if that would make a difference).

The third Jar, (Bigger one) is bleach, with various woods soaking inside. My plan is to wire brush them to remove the softer fibers that have been weakened by the bleach. Then I can treat them with the wash and see how the grain looks.

You can see my tea mixture here also, and the pouring of the Vinegar.

Step 2: After a Couple Days.....

Here is what everything looks like after a couple days. This was actually a really fun experiment. Weathered and old looking in a matter of days!!!

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    30 Comments

    This is a very nice experiment! Thanks for all the info, definitely helps with some projects I'm doing, and jives with some experiments I've been up to.

    I'm a synthetic organic chemist so I thought I'd lend some of what I know and what I've found, and try to troubleshoot a little for people below.

    It's already been discussed, but the desired reaction is the iron acetate is reacting with the tannins in the wood or the tannins you've put there (a little more on that below***).

    If you are just having issues making your iron acetate solution I've got a bit of advice to add to kjbills' below.

    1) If there is any oil or a coating of organic matter on your steel wool, it'll definitely slow up the process a bunch. This includes trace oils from your skin! - Try not to handle the steel wool without gloves, preferably not latex ones.

    - You can rinse off residual oils (maybe from the manufacturing process or something, who knows?) with mineral spirits, then let it dry completely to ensure the surface is free of oils before you begin.

    2) You can really speed up your process by adding some other household chemicals and they shouldn't alter the reaction down the line.

    - To your vinegar you can add a capful or two of a disinfecting hydrogen peroxide solution. This is the safest, easiest way to speed things up, because household hydrogen peroxide is very dilute. Don't use industrial stuff, because that could pose an explosion risk (anything more than say 15%).

    - The intermediary option is to add a capful of household bleach to the vinegar. Bleach is one of the better oxidants available to you in the home and will corrode exposed iron quickly. To give a slight boost to the process, you can again add some salt, but this makes it a little more dangerous because it borders on option three, the most dangerous:

    - In lab, sometimes metals deposit on glassware and you need to dissolve them off. We use a solution of very strong acids, which you should not use. However the gist is this, those acids aren't acting primarily as acids, but also a so called 'radical oxidant': chlorine-radical (or Cl-dot). This is just a very powerful oxidant, and it will corrode iron and many other metals in no time.

    - The only reasonable source of Cl-dot for you is probably from a mixture of ammonia and bleach. This reaction could be quite dangerous because it will generate a small amount of Cl2 gas, do it outside, read below! Place your steel wool as above in a mason jar, add 1/4 inch of household bleach (make sure to wet all the wool, even if it isn't covered), then drop in a capful of household ammonia. Cover the jar LIGHTLY so that it isn't sealed and let it sit for a day or so. Then you can carefully add your acetic acid. The bleach will break down in the sunlight to water and chlorine, and it and the ammonia will quickly evaporate off, leaving iron oxide in solution which will quickly exchange with your acetic acid to make iron acetate.

    EXERCISE REGARD FOR YOUR SAFETY BY WEARING GLOVES AND PROTECTIVE EYE-COVER WHENEVER USING ANY CHEMICAL, ALWAYS DO AND LEAVE EXPERIMENTS OUTSIDE, SO THAT HARMFUL VAPORS CAN'T HARM YOU, ANIMALS OR THE ENVIRONMENT (phew)

    Why use these chemicals???

    Most of the dissolution of iron is probably occurring in a reaction between the thin layer of iron oxide (rust) on the surface and the acetic acid, but once it gets down to the layer of 'elemental iron' as in pure Fe(0), an oxidation reaction needs to take place to make more iron oxide. Acetic acid itself isn't going to achieve this very well; it isn't a good oxidant, and household vinegar probably isn't strong enough an acid to corrode the metal all that much. If you observe this reaction, the oxidant is actually probably oxygen from the air, or radicals generated from UV light so that's pretty slow. You add an oxidant to promote oxidizing the iron and pulling it into solution for/via ion-exchange.

    *** What is going on between the iron and the tannins???

    - Ok, tannic acid (and other tannins) are big organic molecules (http://en.wikipedia.org/wiki/Tannic_acid) made up of highly-oxygenated 'aromatic organic' units. A tree 'uses' chemicals like this (we call them siderophores) to 'grab' iron for various uses (nutrition, antibacterial etc.). Tannic acid is good for this because all of its oxygens have a bunch of negative charge and they can 'grab' onto iron and not let go without necessarily making a bond (we call this an ionic, or dative bond, rather than a covalent bond).

    - When the tannins go out and grab the iron, the entire iron-tannic acid thing is now kind of a new chemical, which we call a 'complex.' This complex is what is colored. The reason it has color is that the iron and the aromatic ligands, share electrons really freely across the entire system: A little bit like a battery (the positively charged Fe) connected to a network of wires. And these wires happen to be attractive to light in that if a photon hits them, they absorb it easily, then share it all around the circuit, and eventually spit it back out as a photon of a different wavelength. Each complex is different, but this one spits light back out as this darker color.

    FINALLY: Why do I care?

    1) If only because I've read this far

    or

    2) At the end of the day it's not IRON ACETATE, but solubilized IRON(II) or IRON(III) that is doing the job. You don't NEED vinegar. Any other iron salt will do. This might be cool, because liquid ammonia also will dissolve iron and ammonia is used to darken wood on it's own. In this way you might see some sort of interesting effects by combining the two chemicals.

    3) Maybe you want to take all of this even one step further. You know that iron behaves in this way, but it's possible other metals will too. Please be safe and research what you are doing, but I've been experimenting a little with solutions mixed with other metals, like aluminum. I'll try to update people if they are beneficial...

    Thanks for the elaborate response.
    I do have some comments and questions.
    The ebonization is I think a complex balance between any leftover acid bleaching the wood, iron(III) reacting with tannic acids to form iron(III) trigallate (a derivative not tannate) and the presence of leftover iron acetate.
    Bleaching will lighten, the iron trigallate is blue to black and the iron acetate is a dulling brown solid.

    I would advise against allowing too much bleaching though am still figuring out if a lack of tannins can be somewhat reliably supplemented later.

    The iron acetate might be dissolved in alcohols but that may also pull them into the wood depending on your concentration and the amount applied.

    If you make an iron acetate solution, adding chems to help the oxidation will only be useful if you have no time to spare.. Otherwise they should be avoided IMO as they can bleach the wood which you will really see in certain parts of the wood.
    Iron acetate has bad solubility in water so as you generate it it will also deposit as nasty brown frothy stuff. What is the point of speeding up the process if it will just reach saturation quickly and deposit?

    I have yet to master the tricks of excess acids and iron acetate precipitation on the wood though..
    Looking for tips on getting out the iron acetate, ebonizing the parts resistent to blackening and info on whether ebonization can overcome all bleached spots...

    Careful with aluminum etc, its toxic..
    Iron(III) might be too though ib different ways i forget

    Love finding the chemists comment on these things. Especially the organic chemists who actually care about educating the public. Thank you for your contribution to the community!

    Thanks so much for this! My solution wasn't doing much of anything and i was about to go buy regular wood stain from home depot...but then i read your post, which was very interesting and informative! I added a splash of bleach and the solution immediately started to change colours...thank you! Science is awesome!!

    Can tannins be added to wood? To pine , for example, to made the color more uniform?

    Great question! I've done some digging into this, as I'm interested in how other people have approached this technique. Tannins are able to be artificially added to wood. The article mentions using Black Tea, which is known to be high in tannins and holds a special place in my house for making homemade wine. However, not all woods will require extra tannin to be added to them. Soft woods, such as pine may require a little extra help.
    -Chemistry student, homemade wine enthusiast, paramedic, honey-do man

    Need to get copper/ patina on alumin I like a little auqua patina mixed in. Any suggestions ?

    Hi there, This is my before and not quit after project.. I love the grey color and I would love to seal it without changing the look..is there a way that I can do this without changing the color? Thank so much!!

    GEDC1119.JPG11850440_1667513173478929_4919335667360295399_o.jpg

    Hi Helen, can you tell me what you used to get the colour on the table. It looks great and just what im looking for on a set of pine shelves. Hope its not too long ago. thanks Peter

    http://www.homedepot.com/p/Varathane-1-qt-Matte-Soft-Touch-Polyurethane-266233/203331997