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The Myrtlewood
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Putting the Pressure On by Richard Yost Gareth Mast is an impatient man in no particular hurry. When he's not helping his wife, Sharon, at her Myrtlewood Gallery in Reedsport, Oregon, he's likely to be found in his shop turning his elegant maple burl bowls. He says he is in no hurry to ever go into production turning where he would have to produce more than the dozen or so "signature-quality" bowls he does each year, the kind that have made it into a number of nationally juried shows. While production turning may not be in his future, Gareth has, nonetheless, spent several years developing a way to eliminate that universal bottleneck in production turning...the years-long wait for green turned bowls to dry. Gareth's impatience with waiting for Mother Nature to get around to drying his roughed out bowls is shared by a lot of woodturners, as witnessed by all the chemical, electrical, and mechanical attempts to quickly bring a green, rough-turned bowl down to a stable dryness. The trick, of course, is to dry the wood without warping the bowl into something that looks like the victim of an elephant stampede. Gareth's trick? Pressure cooking. "A few years ago a friend was telling me how he was pressure cooking some pieces of wood to kill the bugs that had infested it," he explained. "I had also heard about gun stock blanks being cured or dried in pressure cookers, so I thought 'Why not try it on green-turned bowls?" Gareth found the largest pressure he could--a 16 incher made by All-American Pressure Cookers--and started experimenting. "A good rule of thumb for curing wood naturally is that it takes about one year for each inch of thickness," Gareth explained. "With pressure cooking, I figure about one hour per inch on a roughed out, green bowl, which makes the process particularly helpful to me as I generally turn rather thick bowls that are two or three inches thick. After cooking, the bowls are hung up for about three months to finish dry. "Over the years I've tried all kinds of ways to work and dry my bowls. I've been experimenting with pressure cooking for a little more than two years and it works great." After rough turning a bow, Gareth puts the piece in his pressure cooker, pours in a couple cups of water, and cranks up the heat. During the winter he uses a wood stove that also heats his shop. In the summer or if he's in a hurry, a propane stove is used. He warns that if propane is used inside to be sure to have plenty of ventilation. While he was experimenting, Gareth stumbled on something that makes for some very unique turnings. "When you put a bowl into the cooker it is best to first put in some small pieces of wood to raise the bowl up off the bottom so there is no chance of it becoming discolored where it touches the metal bottom," he explained. "One time I put in some pieces of manzanita (a dark red) root. After cooking, the maple burl had taken on a lustrous, very distinctive reddish tint that really highlights the grain. The color penetrates deep into the wood because it is still there after I've done the final turning . I now add manzanita chips to most of the bowls I treat." Bowl size and wood density and thickness do influence the amount of time a piece is pressure cooked. After putting in the wood chips, the water, and a rough-turned bowl, and carefully screwing down the pressure cooker lid, Gareth turns on the heat. He starts timing when the pressure reaches 15 pounds per square inch, and cooks the piece about one hour for each inch of thickness. Most pieces stay in the cooker for about three hours. "About the only drawback I've found is that occasionally a bowl will warp way out of round, but that's rare. As these are all rough-turned bowls there is always plenty of wood left that can be taken off to bring the piece back into round.." He adds that one other shortcoming is that his 16-inch diameter pressure cooker limits the size of his bowls to about 15 inches. However, larger pressure cookers are available through kitchen and restaurant-equipment outlets. Once the cooking is done the bowl is removed from the cooker and quickly dropped into a tub of water, which helps prevent checking by quickly cooling down the wood. A warning: Gareth cautions anyone using a pressure cooker to be sure to bleed off all the pressure through the relief valve or by cooling and to make certain the pressure gauge reads zero before attempting to take off the lid. Even a pressure of two or three p.s.i. is enough to send the heavy metal lid flying. Be very careful in taking the lid off, as escaping steam can badly scald and unprotected face or arm. He strongly advises wearing a long-sleeved shirt or jacket and gloves to prevent being burned or scalded. Anyone who has ever tried to get the bark off the moonscaped top of a maple burl will appreciate what happens next. "The steam and sudden cooling do a great job of loosening the layer of bark on the burl," Gareth said. "Quite often it just lifts off in one piece. Not only does that eliminate hours of power washing, scrubbing, and picking, but the surface of the wood is left with a rich satin luster that needs no more work."
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The Myrtlewood Gallery |