{finishing} How to oxidize wood

How to what? Oxidize? What does that mean?

Oxidized wood is just wood that has weathered, or been made to look weathered.

Weathered wood has a patina that commercial stain and other finishing applications can't match. But since it doesn't make sense to build a piece of furniture and then leave it out in the elements to weather, this quick process of oxidation using steel wool and vinegar is a great substitute...and looks just as beautiful, but without the splinters.

An oxidizing solution comes in handy when you're working with reclaimed wood like I did in these projects:

 

When you're cutting reclaimed wood, you end up with fresh-looking wood on the cut ends. Keeping an oxidizing solution around is an easy way to make the newly cut ends match the rest of the old wood.

An oxidizing solution also works on new wood, and can even be used on hardwood floors.

Here is how I oxidized the project I worked on most recently, the X Coffee Table. I also used it on the X End Table and the X Console Table.

Step One: Create the oxidizing solution.

Grade #0000 steel wool and white vinegar are what I use in my oxidizing solution. Some people use nails or screws, but I have found that super fine steel wool works well for me. I put one hunk of steel wool (I tear it up first to make it oxidize faster) into a glass jar and then fill the jar with vinegar. I let the solution steep for a few days, shaking it occasionally. As the steel wool dissolves, the solution will occasionally bubble when I shake the jar.

This jar of oxidizing solution is about eight weeks old. It darkens as it ages.
Edited to add: your jar will not look rusty like mine until your solution has
been sitting in the jar for a long time. When you first make your solution
it should be a grey-ish color with some solids on the bottom and murky
vinegar on top. 

I keep a jar of this solution in my garage and use it frequently. If it sits for long (like more than a few weeks) it becomes super concentrated and starts to turn a rust color. Depending on the species of wood I'm oxidizing, that rust color can impart a tone to the wood that is warmer than I like. If so, I simply water down the solution with vinegar (up to two parts vinegar, one part oxidizing solution depending on how concentrated the solution is) and it seems to work fine. Depending on how much of the solution I use, I can continue to water down my solution for at least a few months or up to a year before I need to start over again with fresh steel wool and vinegar.

Step Two: Brew some STRONG black tea and paint it on your piece.

This tea isn't for drinking. You're brewing it to impart more tannins to your wood. Some wood, like the cheap whitewood I use in building rustic furniture, has very low levels of tannins. In order to get the weathered look, your oxidizing solution needs tannins with which to react. Oak, cedar, redwood, and fir have relatively high levels of tannins. Pine, on the other hand, does not so it requires a generous coat (or two) of black tea.

When I put the tea on, I try to keep it only on the wood that I know needs tannins added to it. If I'm not familiar with the wood I'm using, I test some scraps: slap on some oxidizing solution and see what happens. If it doesn't change color, I try a new piece. Brush on some tea, let it dry, brush on some oxidizing solution and see what happens.

I find that these mini-experiments are a great way to entertain my kids.

Once you've got a good coat of tea on your piece, let it dry completely before moving on to the next step.

Step Three: Paint on your oxidizing solution.

Now that the tea is dry, you can paint on your vinegar and steel wool mixture. A synthetic bristle brush works well for this application. The fumes from the vinegar and steel wool mixture are not harmful but not particularly pleasant either, so I try to use it in a well-ventilated area. The color of your wood will change gradually as the solution reacts with the wood.

Step Four: Lightly sand to even out the color.

For projects like the X Coffee Table and the X Console Table, the plans call for several different dimensions of wood and most of those different dimensions (2x2, 2x4, 2x6, 1x12) come in different species. The 2x4s tend to turn black when I oxidize them while the 2x2s barely turn grey. The black tea helps with this but, even with a coat or two of tea, the 2x4s usually end up darker than the rest of the piece.

To even out the color, I wait until the oxidizing solution is completely dry and then I give the whole piece a light sanding. I use 220 grit paper on a sanding block or wrapped around a sanding sponge. The amount of sanding I do depends on how much of the color I need to take off. The 2x4s get lots of sanding, the 2x2s get very little -- just enough to smooth out any rough spots.

Step Five: Seal it.

Just like sealing stained or painted wood, sealing an oxidized piece will deepen the color and enhance the grain pattern of the wood as well as protect the finish. I've experimented with pure tung oil, polyurethane, polycrylic, PolyWhey (usually my favorite sealer) and wax over a weathered finish. My favorite, by far, is wax. Not only does wax feel really nice (silky smooth) and give nothing more than a subtle sheen, but it also maintains the integrity of the weathered color. Where tung oil and poly finishes bring out a warmer, orangey tone in the wood, wax keeps the wood essentially the same color as the weathered finish you've worked so hard to create, just with more depth. (Edited to add: Vermont Natural Coatings has recently come out with a wipe-on PolyWhey in satin that I love. It is a more durable alternative to wax, non-toxic, has no scent, and only deepens the color of this finish. If you're looking for a hard, long-lasting topcoat for this finish, wipe-on PolyWhey is it. Vermont Natural Coatings isn't paying me to say this...I just really, really love the stuff.)

I always try to use the lowest-VOC finishes available, but I have not yet found a no- or low-VOC wax that I'm totally happy with.  So, I save most of my VOC inhalation for Briwax. I use it in a VERY well-ventilated area. For this finish I actually only use a tiny bit of Briwax mixed with bowling alley wax (the yellow can in the photo above) which seems to be less volatile than Briwax. I really love the bowling alley wax -- it is super easy to work with. There is also a brown version of the bowling alley wax, but I haven't tried it yet. (Edited to add: I haven't tried CeCeCaldwell's wax yet, but it's on my list. Since I wrote this post, I've stopped using Briwax because the fumes make me too sick.)

For this finish, I want to add just a tiny bit of brown to the wood to warm up the tone without letting the wood go orange. A touch of brown wax seems to do the job, plus it adds color to any tiny holes in the wood that the oxidizing solution missed. So, I dig out a good hunk of the bowling alley wax and slop it in an old yogurt container. Then I add a tiny bit of brown to it. The day I did this was a hot hot hot day (at least for Colorado it was hot) -- like over 95 degrees -- so the wax was melted and easy to mix. In the middle of winter it wouldn't mix quite this well.

Once the wax is mixed, find a soft old rag you never want to use again, dip it in the wax, and apply a very thin coat of wax with the grain of the wood. The wax usually dries within a few minutes and then you can use a clean, soft rag to buff the wax to a subtle shine. The faster you buff, the shinier it gets.

Adding another coat or two of wax will help protect the piece, but you'll need to give the wax ample drying time between coats. If the wax hasn't hardened yet, you'll notice that with each new coat of wax you take off some of the previous coat.

In my experience, the clear bowling alley wax seems to dry to a harder, more impenetrable finish than straight Briwax. It's also cheaper and less stinky. :)

To clean a waxed finish, I think it is best just to use a slightly damp or dry microfiber cloth. Vinegar-based cleaners and other household cleaners tend to strip wax. To rejuvenate the finish, just add another thin coat of clear wax to the piece and buff it out. As you build up the surface with multiple thin coats of wax, the surface gets more and more durable. (Edited to add: I've recently found that Howard's Feed-n-Wax is great for maintaining a waxed finish.)

An oxidized finish requires a little change in how you think -- there is no ready-made can or in-store sample to show you exactly what color you'll end up with. But, with a bit of experimentation you'll end up with a lovely piece of furniture with gorgeous silvery tones that can't be created any other way.

Pssst...check out what happens when you oxidize in sub-freezing temps. Take a deep breath, and remember that this is art, not science.