Interesting Apple wood feature

[Owd Jockey]

I've had a piece of Apple trunk hanging around in the shop for while, but a few radial cracks made me decide to do something with it. I cut it up in sections intending to turn a few small shallow dishes. Unfortunately, at the Sapwood demarcation, i.e the Sapwood/heartwood interface, a thin membrane (possibly made up of 'extractives') formed a smooth transition allowing the heartwood to simply come away. The membrane is not fungal and the black marks on the wood is simply metal coating from the steel wedges while cleaving the piece. I cannot remember ever seeing this before. Anyone else ever come across this?

 

[niall Y]

Don't know about the staining but it appears to be a cup-shake, I've had joinery quality redwood , where the centre of the stock has come completely away. Though if the piece fits neatly in position you can glue it back in place.

 

[Sgian Dubh]

Like niall Y, I suspect it's a cup shake. If it completely encircled the trunk it would be a ring shake. The causes or cup and ring shakes are varied; it may be due to sever flexing of the stem during high winds or because of old age and, more often than not, the shake forms in the region where sapwood is turning into heartwood. Any weakness between earlywood and latewood can be exacerbated by other factors such as bacterial infection. In this case the bacteria get a foothold by entering through the tree’s root system. The bacterial infection characteristically spans many growth increments either side of the shake. Slainte.

Above. Cup shake in an American ash board.

Above. Cup and star shakes in a Leylandii trunk felled just a few days earlier.​