Читать книгу Ellsworth on Woodturning - David Ellsworth - Страница 15

The question is this: What do you do to preserve your materials once you have them? This is where the furniture makers have it over us turners. They can select their boards well in advance and stack them in almost any enclosed space where the temperature and humidity are reasonably constant. Turners– especially those of us who turn green wood–often face a feast-or-famine situation where we have to contend with entire logs, roots, or burls. How do we control the cracking or rotting that occurs in the time it takes to turn up an entire log?

The easy answer is to invite a bunch of friends over and share the log. This is a common practice with the turning clubs that exist both privately and as affiliates of the American Association of Woodturners. Opening up a tree is like cutting a hole in the roof of your house: Nasty things can happen. So, short of leaving the log whole, the first thing you want to consider is what you wish to do with the material.

The most common practice is to block up the log into desired shapes using a chainsaw and then coat the end-grain surfaces with a couple of coats of wood sealer, such as Anchor Seal. Painting or waxing the ends of the blocks doesn’t work very well, because as the wood shrinks over time, it pushes moisture out of the end grain, which lifts the paint or wax right off the surface. This is not a problem with wood sealer, as it both sticks to the wood and breathes to slowly let the moisture through.

The next step is to store the blocks in a cool, neutral climate, out of the sun and wind. Garages and barns are ideal because they’re easy to back the truck up to. Air-conditioning in any space is evil for both green and dry wood, as it will draw moisture too quickly out of the wood.

If your intent is to turn the blocks up within a few weeks or months, wrapping them in plastic bags is another good solution because it completely isolates the blocks, not allowing any moisture to escape. If you’re bagging fresh-cut green wood, be careful not to leave the blocks too long, or mold and rot can occur.

In hot, dry climates like the desert, bagging is the only way to save solid green blocks. Some people will even buck up a tree and bag it on site just to keep it from cracking in the truck on the way back to the workshop. Others will spray the bagged blocks with water while they’re turning the form just to keep moisture levels high. The constant heat and aridity is why so many turners in these climates have gone to making segmented turnings. Tiny pieces of wood that are already kiln-dried and glued together don’t exhibit any significant change in shape, with the result that any overall form movement in these extreme climates is very minimal.

In colder climates, freezing the logs is the best option. My first experience with freezing wood was when I lived in the mountains of Colorado from 1977 to 1981. This was the period when I began working with green wood. It was obvious that solid green blocks and logs (when I could find them) wouldn’t last long in the dry and frozen winter climate at 8,500 feet. My answer was to pack them in snowbanks during the winter and dig them out as I used them.

Where I now live, in the more humid climate of Pennsylvania, I am blessed with dense hardwoods. I can leave my logs whole under the canopy of the forest, where they don’t get much direct sunlight; they’ll stay in good turning condition for quite a few months. An added plus for me, because I enjoy working with spalted wood (see “Spalting wood” on page), is that the combined heavy leaf cover, moist climate, and high humidity make it easy to spalt wood in a few months. The difficulty I have is woods like silver maple spalt so quickly you can hardly get through a tree before the whole thing rots. But the exciting part is while I’m working my way through the log, the designs of the pieces I make vary as the wood's condition changes—the first piece being made from fresh-cut wood and the last from heavily spalted wood.

“When it comes to preserving the materials you have, your most important task is to figure out how to minimize change.”