Got a wind fall of Eucalyptus couple of weeks ago, and promptly cut it into bowl blanks and end sealed it. I turned a couple of roughs and end sealed them inside and out. Got back from vacation and the bowls were trying to turn into pretzels, with rim cracks of 1 inch depth. Re rounded one and threw it into LDD overnight. Yesterday I tried to finish it, but it started moving while sanding. Turned into a potato chip instead of a pretzel. This is real energetic wood. Have a picture posted on ABPW along with a picture of a piece of bowl blank that I sawed off and end sealed on both ends 2 weeks ago.
Well, considering that the grain is going in several directions (looks like it could be a crotch piece) and there are two knots, it's not totally surprising there's that much movement happening with this bowl - in addition to whatever amount of shrinkage may be normal with eucalyptus.
My server finally updated abpw. Looks like you have a fine "art" piece there. If the stuff's going to be squirrelly, make a virtue of it by cutting thin while green and letting it go.
As to the end coating, it looks like you took the bark off, which is a no-no if you're trying to keep the log. Also looks like you had a wind shake to help the piece split. The mildew you see on that piece, which dried pretty rapidly, is the reason I gave up on coatings almost immediately. That, and the fact that my control pieces came out as well, and without mildew. Unfortunately, I was turning some curly maple at the time, and the mildew ruined the several test pieces.
Never having used eucalyptus, only suggestion I can offer is not to have such vertical sides on your roughed bowls if you're looking to avoid rim checks. If the sides slope in, they tend to relieve a bit by turning down. Normal drying tension is caused by the faster-growing earlywood contracting more than the latewood - dark part of the annual rings. That, and as you can see in the coated piece, the fact that chemical and physical changes have taken place in the heartwood, keeping it dryer, usually result in radial checks from outside in in the log. In the bowl they pull down the edges, often opening up the small radius rings near center.
There are many types of eucalyptus, or gum, trees. Some are well-suited for lumber, others not. It's my understanding that gum trees were imported into California for lumber, but oops!, they were of the not-good-for-lumber variety, and also grow like weeds, hence their presence all over the dang place. That variety grows so fast that it is very weak. My mom was almost killed by a huge branch which fell just behind her car.
Only took the bark off to cut the circle for a bowl. Saved one end for the piece you see. The Outer portion did not crack. It is also the part which mildews easily. Higher sugar content? Lower tannin content?
The bowl continues to deform, looking more and more like a potato chip. My wife likes it, but I have given up on leveling the bottom until it completely dries.
Looking at this bowl, it's not particularly surprising it has moved so much as it appears the grain is going in multiple directions plus the presence of two knots. I don't know the shrinkage characteristics of straight grained, clear eucalyptus, but the "features" in your bowl certainly don't help matters.
Sure, sapwood has more moisture, and that's what encourages mildew. It's a strange organism that can survive on what the air brings it, so I'm not sure sugars make a difference. Note it's growing under and on wax. Sure makes a mess of light woods.
Bark on is the way to keep the radial checks at bay. End checks are pretty much self-limiting, so a lot of folks leave a whole log, lopping off a fresh chunk to turn when they have time, versus taking chances on a bunch of blocks.
Then there are those stupid enough to split firewood without looking, who end up with badly fragmented pieces of heavily curled maple rather than big beautiful bowl and platter pieces.
They are a step up from the ornaments I've been turn> > My server finally updated abpw. Looks like you have a fine "art" piece
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