|Project by Stonekettle||posted 11-17-2015 08:39 PM||794 views||0 times favorited||6 comments|
Sitka spruce burl
Probably one of the toughest pieces I’ve ever turned, simply because I kept expecting it to disintegrate.
The burl I cut this from was large, about 4 feet across, and dry-rotted throughout the center. It was taken from a tree that had been killed by invasive spruce bark beetles (a continuing problem here in Alaska). I have no idea how long the tree had been dead before the wood was harvested, likely years. The burl sat outside in the elements for at least a decade and then dried in my shop for another two years before I cut it up into blanks. Then it dried for another year. What solid wood remained was very soft, like balsa, and was laced through with lines of spalt and veins of dry rot.
Turning it required low speed and a VERY sharp 5/8” Irish grind bowl gouge – which I sharpened on a low speed aluminum wheel, then stropped on a leather/glass wheel, and finally dressed with a 10,000g diamond hand hone. The cutting tool had to be that sharp, literally sharper than a scalpel, or the soft fibers of the wood would just tear and crush instead of slicing cleanly through the dry rotted areas – which had the consistency of old dry sponge. To hollow out the inside, I had to wrap the bowl in painters tape to keep it from flying apart. After it was turned, I carefully sanded away most of the soft dry rot to exposure the spalt stained figure underneath. Then the whole thing was soaked in stabilized oil, which when dried hardened the wood. Then the whole piece was sanded at low speed on the lathe to 600g. Oiled again and waxed. And finally mounted on a polished walnut base. It’s about 15” in diameter.
-- Jim Wright, Stonekettle Station