Staining wood to give it a darker, richer color is an age-old practice; while methods have improved, staining still has drawbacks.
Since stain mostly sits on the surface, a mishap can easily scrape it away to expose the natural color of the wood beneath. Furniture parts such as chair and table legs are quite vulnerable to such damage. What’s more, stain will usually be absorbed more readily in some areas than others, and without careful surface preparation, stain will accentuate small imperfections such as sanding scratches, tear-out, and uneven porosity.
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Darken wood without staining using Martin Goebel's creative tanning bed approach.
Ammonia fuming is a practical alternative to staining – provided you are working with oak, beech, cherry or butternut. In this process, the fumes given off by aqueous ammonia do all the work for you; they react with the naturally occurring tannic acid in the wood to darken it.
Most commonly associated with oak, which gives the most dramatic results, fuming with ammonia has origins in medieval Europe where livestock barns were typically built with oak timbers. Over time, the oak woodwork near livestock always darkened. As anyone who has spent any time in a hog barn knows, livestock manure can be a rich source of the pungent gas. Eventually, some curious woodworker realized what the active ingredient was (ammonia) and put it to use.
By the beginning of the 20th century, the process had evolved to the point of commercial application by Gustav Stickley, who manufactured Arts and Crafts-style furniture (primarily using white oak) in the United States. The characteristic color has become so closely associated with the style that it’s difficult to imagine a Morris chair finished any other way.
The photographs of the footstool shown here demonstrate a typical degree of darkening in a fumed-oak furniture piece. What cannot be seen in the photographs is how far the color has penetrated the wood. Typically, the wood will be darkened as much as 1” deep on the end grain and between 1/16” and 1/8” deep on the face grain, permitting a workpiece to be trimmed to final length and lightly planed or sanded after fuming, without affecting the color.
While the process of fuming a piece of furniture is simple, working with ammonia requires special precautions described by Lee Valley Tools.
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