Back in March I rough turned a series of bowls from newly felled pear. The wood was beautiful to turn, not large in diameter. I made a variety of shapes, and thicknesses. In some I left the heartwood, and others i didn't.
By now even the thicker ones have dried out and are ready for finishing. Today I finished one of them, and this is the result.
My technique is to turn green and to use the warping of the wood as a feature in the finished bowl. This was cut along the grain, so the sides shrank back more than the length, making an oval. But the other effect of the shrinkage is to distort the rim into a boat shape.
Which is exactly what I wanted. But although I could finish both the inside and outsides of the bowl whilst holding it in the lathe, I couldn't finish the foot - because that was how it was held.
Normally, with a flat rim, I would mount it on a faceplate with button jaws, no problem. But this rim was so far off the plate that the buttons wouldn't grip. The answer was to double them up.
It worked. Though because of the oval distortion some of them gripped and others didn't.
But I was able to clean up the foot.
As for the spiral?
Pear, like many English woods, changes colour when it is felled. The sap oxydises and the wood darkens. This is a surface phenomenon, though as time goes on the darkening penetrates further.
On the timescales I am working with, the oxidisation is superficial. So if you cut through the surface layer you get the original colour of the wood.
When I rough turned this bowl, I deliberately dragged the chisel across the inner surface making a deep spiral cut. Then, when it had dried out, I sanded off the tops of the ridges made by the spiral grooves, exposing the colour of the wood underneath. Hence the pattern.