By David J. Marks
Fuming wood is a technique that was widely used during the Arts & Crafts movement in the early 1900’s.
Gustav Stickley preferred fuming because it really accentuates the medulary ray fleck pattern that quartersawn white oak is known for. The “fumes” in fuming are ammonia vapors that emanate from 26 percent aqua ammonia.
The way the process works is that the piece of furniture or object to be fumed is placed inside a tent, and then the aqua ammonia solution is poured into a glass or plastic bowl and also set inside the tent. Once the tent is sealed, the liquid will continually release ammonia vapors filling the tent. The vapors will chemically react with the tannic acid in the wood, causing it to change color.
The story has been told that this technique was discovered after someone who had stored white oak in a barn and then began working with the wood, noticed how much darker the oak had become. Anyone who has spent any time around horses or cattle knows how powerful ammonia fumes are.
Building a tent to fume the wood is not that difficult. I made a wooden frame tent that could be disassembled after use, and covered it with 4 mil plastic. I used this tent for several years but then decided it was simply faster to set up some saw horses, place a couple of 2 by 4’s on them and drape some 3 or 4 mil plastic over it and seal it with duct tape.
Safety is the most important consideration if you are thinking about trying this technique. You will need a face mask respirator with ammonia filtering cartridges. These types of cartridges can be found at safety equipment stores which are usually listed in the phone book. I also recommend chemical resistant gloves and goggles for the eyes.
Typically I do all of my fuming outdoors on an area that has a concrete slab and an overhanging roof. When I am done, I cut open the plastic tent, remove the piece and leave the area until the fumes dissipate.
Fuming works well on white oak due to the levels of tannic acid that naturally occur in the wood, but I have also had success fuming mahogany. Another method is to apply tannic acid (which is available as a powder to be mixed with water) by brushing it onto woods (that do not contain it naturally) and then fume those pieces.
As I have recommended with all finishes, do test samples, recording the information on the back and keep in mind that the color will become darker when the wood had been finished with linseed or tung oil.