Fuming Wood with Ammonia
Chris Gochnour explains how to darken wood without touching it.
Synopsis: When you see wood that has been stained or dyed, you know right away that it’s been stained or dyed. But fumed wood looks natural, as if it came from the tree with that dark, rich color. Chris Gochnour explains what you need to do to fume wood with ammonia and how to make a vaporproof tent to house the fuming process.
Using ammonia fumes to alter and enrich wood’s natural color, a process called fuming, has been a staple of woodworkers for centuries. Its effect is quite distinct from other coloring techniques. When you see wood that has been stained or dyed, you know right away it’s been stained or dyed. But fumed wood looks natural, as if it came straight from the tree, but with a darker, richer color. I have been fuming furniture for more than 30 years and love the natural, honest, and woody tones it imparts.
Ammonia fumes react with the natural tannins in certain wood species to deepen the wood’s color and enliven the figure. Woods high in tannin—such as white oak, beech, and butternut—respond best to this treatment. The ammonia fumes penetrate the wood uniformly and deeply (to a depth of about 1/8 in.), so fumed pieces can be sanded without fear of sanding through the coloring.
What you need to get started
Fuming requires ammonia, plastic containers, and a fuming chamber. Since household ammonia is fairly weak at only 5% to 10% ammonia, I use a commercial aqueous ammonia (also known as aqua ammonia or ammonium hydroxide) that is a potent 25% ammonia mixed with water. You can purchase commercial-grade aqueous ammonia online, or at some janitorial supply stores.
I use plastic containers to hold the ammonia and build a vaporproof tent, or chamber, to house the fuming process. I typically build the frame out of wood and wrap it in clear polyethylene sheeting. I’ve used a 5-gal. bucket to fume small pieces. For really large pieces, I’ve portioned off a section of my finish room with wood framing and polyethylene tarps. I once did this to fume a dining table and eight chairs all at once. My finish room’s fan made it ideal for venting the fumes when the process was complete.
From Fine Woodworking #282
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with Ben Strano
SEPTEMBER 1, 2007
MARCH 25, 2020