Woodworker's Journal 2011-35-Winter, страница 36
Fuming Wood Darken oak and other tannin-rich woods the classic way with ammonia. Gustav Stickley popularized the Craftsman, or Arts and Crafts, style in furniture and, with it, fumed oak. He preferred quartersawn oak, believing it to be stronger and more stable, but disliked the distinct appearance of ray cells, which only got more pronounced when the wood was stained. Today, we prize that figure and call it "tiger stripe," but Gus wanted to minimize it The one way he found to darken both the vertical and ray cells was with ammonia fuming. As a result, fuming oak fascinates many hobby woodworkers today, even though the Stickley Company, which is back in business, does not fume at all anymore. How it Works Fuming is chemical staining that occurs when tannin in wood reacts with ammonia vapors. Ammonia colors woods that contain tannin, but not those that don't. Predictably, the higher the tannin content, the more dramatic the color change. That's why sapwood, which is low in tannin, does not change color as much as heart-wood, and why white oak, with its higher tannin content fumes more dramatically than red oak. Typically, you place ammonium hydroxide, or liquid ammonia, in an open container within a closed filming booth. As the ammonia evaporates, it forms two gases, ammonia (NH3) and water vapor. The active ingredient in fuming oak is ammonia gas, not ammonium hydroxide. That's why wood darkened by fuming looks different than wood darkened by simply being wiped with liquid ammonium hydroxide. Fumability Factors Fuming is not just for oak. Any wood that contains tannin will get darker when fumed, including oak, walnut, mahogany, chestnut, ash, cedar and cherry, to name a few. Woods low in or For small pieces the author recommends a Rubbermaid container sealed with duct tape as a fuming chamber, but safety gear is a must. Plastic pipe tents break down easily to change size and shape. A thermometer and heat lamp let you hit the right temperature. 36 Fuming Wood |
