…wood, that is! A week or two ago, Don mentioned something about posting my fuming techniques and experiences. I finally got around to writing a little something up on it.
My desire to experiment with fuming wood stemmed from my love of Arts and Crafts design and construction techniques. I don’t have any finished pieces yet, but I’ve been working on some design ideas that take Arts and Crafts design elements and incorporate them into smaller pieces. My shop time is at a minimum right now, because of other obligations, but once spring hits, that will be my main focus.
Anyway, one of the first techniques I read about was ammonia fuming. It interested me mostly because I’m not really a big fan of the lighter finishes I was putting on my oak pieces and I try to avoid using stains and dyes when possible.
Somehow, fuming with ammonia seems different to me. It brings out a rich, dark color without muddling the finish. And aside from the one big issue of dealing with a somewhat dangerous chemical, it can’t get much simpler!
My first few trial runs, with common household ammonia, were pretty much unsuccessful. I’d read it didn’t work that well, but I had to try it for myself. After fuming test pieces for 24 and 48 hours straight, using ideal conditions and following through with the post-fuming processes, my sample pieces only showed a marginal darkening – it was hardly worth the effort.
So I had to track down some more powerful ammonia. A little bit of research indicated very few places where a higher percentage of ammonia could be obtained; one of those places was printing companies (it is used for a printing technique specific to blueprints). After a few calls, I located a local company who sold me a 2-gallon bottle of Anhydrous Ammonia for about $9.
Anhydrous Ammonia precautions: I’m listing some of the basics here – you can find more detailed precautions on-line with a quick Google search. Do not store containers containing Anhydrous Ammonia in any location that can get too hot (over 85 degrees). Do not store this chemical in a metal container (this includes glass jars with metal lids, for all of you people in Rio Linda), as it will corrode the metal and you will quickly not have an air-tight seal on your container. Wear NH3-rated goggles, gloves, and cover as much exposed skin as possible. Never wear contacts when dealing with Anhydrous Ammonia. Overexposure to this chemical can lead to unconsciousness and even death. (I suppose that can happen to a lot of chemicals, though…)
The first time I used this ammonia, I was outside. I did wear a mask and goggles, but I didn’t wear rubber gloves. Though no liquid actually touched me, I had a cut on my right hand that started burning because of the fumes. This is powerful stuff. You have been forewarned.
The Fuming Experiment
Now that I had the right ammonia, I wanted to run some more test samples. But I decided to run a gamut of species through, just to see what happened with each one. So I ripped some strips of White Oak, Honduran Mahogany, Black Walnut, Black Cherry, Bubinga (I had to get something from the rosewood family in there…), and Hard Maple. All were sanded to 150 on two sides and 220 on two sides, and marked accordingly.
I fumed all of the test strips for 24 hours. (I’ll go over what I use for a fuming container later on.) I figured that was a good base timeframe, since that is how I’ll fume most of my pieces. I usually only have time for woodworking in the evenings, so I wouldn’t be able to pull something out eight or 12 hours later.
After fuming, I laid the test strips out on my workbench to off-gas for 24 hours. (Once the pieces have off-gassed, I can barely smell any trace amount of the ammonia, if anyone is concerned about that.)
At first glance, there were noticeable changes in almost every sample stick, though in each case I could not really determine a difference in color between the 150 grit and the 220 grit sides.
White Oak – Very bland, gray-colored wood at this point. This was to be expected.
Honduran Mahogany – Rich, darker coloring. Second-most notable change in color.
Black Walnut – Well, it did get a little darker… and somewhat gray-ish.
Black Cherry – Dramatic change in coloring – much darker!
Bubinga – This strip was darker and a little less colorful.
Hard Maple – There was not much noticeable change here, if any.
The next step was to apply a coat of BLO (Boiled Linseed Oil) to each test strip. Here is what I noted after it was applied…
White Oak – There’s the color I wanted! I’d read the darker color doesn’t pop until the BLO is applied. This was so true! Stickley knew his stuff!
Honduran Mahogany – The mahogany turned a wonderful reddish-brown color. I don’t miss that orange-glow look!
Black Walnut – Even darker still, but with rich coloring – may be useful for something similar to an ebonizing effect?
Black Cherry – The BLO made an even greater improvement upon the coloring of the cherry. This is great for darkening cherry without a hint of blotchiness and it is a whole lot less messy than using lye, which is what my friend Scott uses.
Bubinga – Very brown, almost more like a Machiche or Chechen at this point. I probably won’t fume Bubinga again… I’d just use Machiche or Chechen, you know?
Hard Maple – Looked like I’d applied BLO to some hard maple, to be honest with you.
After the BLO dried, I cut the test strips in half, to check the depth of penetration into the wood. It looked like the ammonia chemically changed the wood down to about an 1/8th of an inch, give or take a bit. That is plenty of depth to not have to worry about sanding through it, for the most part.
A test I plan on running in the near future is with Kauri wood. This is part of a deal I made with the owner of Ancient Woods. He sent me some sample pieces; I agreed to fume some of it and send some of the test pieces back to him.
I will also try fuming a few other species of wood when I do that. I’ve picked up a few pieces of Santos Mahogany. I have some reclaimed American Chestnut, which I have a feeling will react in a similar way to the white oak, and some beautifully figured (quilted) Box Elder. Box Elder is in the Maple family, but I’m trying to get a slightly darker look to it and have not been terribly successful with staining or dying it, so I thought I’d give fuming a try.
The Fuming Tent
I tried messing around with a frame and 4mil plastic. It was just that – a mess. I suppose with some thought, you could come up with a fuming frame that broke down and stored somewhat easily – but I didn’t care to give it that much thought. 90% of my projects are smaller projects, so I started thinking about it. What do I own that is already air-tight and big enough to fume small boxes and pieces? Then it struck me – my old Igloo cooler that got pushed by the wayside after my purchase of one of those cool 5-day coolers!
It worked like a dream. First, I poured the ammonia into a plastic Cool Whip container and set it in the bottom of the cooler. Then I placed the plastic open-weave basket that came with the cooler upside down on top of the Cool Whip container. Finally, I set all of the test strips inside the cooler and shut the lid.
When it comes to fuming, the hotter the better – you’ll get a much better reaction with the ammonia at warmer temperatures. I wouldn’t recommend fuming below 70 degrees Fahrenheit. With the cooler, I can fume out on the deck, under the deck, or even in the garage if I need the extra heat. When fuming in the garage, I just make sure to set it all up outside and then carefully carry the cooler inside.
Things To Keep In Mind
I dispose of the ammonia by pouring it back in the main ammonia container. This 2-gallon bottle will last me a very long time. If you don’t want to do that, then dilute it with about a gallon or two of water and feed it to your plants! They’ll love it!
You can fume your entire piece, unassembled, and then glue it up and finish it afterwards. The chemical reaction does not have any effect on the wood’s ability to accept glue. So you can fume your frames and panels all at once and then glue it all up with no worries about an unstained edge showing up at a later date.
Actually, the ammonia gas will get in to most every nook and cranny on your piece, so you could actually glue up your frames and panels and THEN fume them. Guess what – you still won’t have to worry about an unstained edge showing up at a later date.
If possible, try to use boards from the same tree (or just the same board) in your project. Different trees might have different levels of tanin in them (that’s the chemical reacting with the ammonia) and the wood will react accordingly.
To fume woods with little tanin in them, you can always try adding it! Brew up some tea, let it cool, and then brush it on and let it dry! The inital application might darken the wood a little, but you’re supposed to be able to get it even darker with fuming at that point! This is something I’ve not yet tried. I might try it with the Box Elder…
If you’re really ambitious, and want to fume something as large as an entire bedroom set (believe me, it’s been done), then consider renting a moving truck! A bit of duct tape and some 4 mil plastic, and you can create a fairly large airtight room. Once you’re done fuming, just open the truck up and let it off-gas for a few hours before returning it to the rental place!
-- Ethan, http://thekiltedwoodworker.com