My firewood supplier obviously deals with a lot of old and fallen trees, and these will sometimes have interesting colouration caused by fungii known as spalting. This can be simply colours such as yellows, pinks and purples, or in the case of this bowl the more classic black lines which is a mineral deposit. The dried wood is quite harmless to humans.

So sometimes when I am fetching a bucket of logs for the stove I will hesitate and think to myself "Looks like there might be a bowl hiding in there!". The wood is kiln dried, so very stable, but the accelerated drying process sometimes means a fatal crack will exist. The worst case is that I get some turning practice, and the thing ends up on the fire anyway (plus a bag of shavings for a friend's chickens to use as litter).

The fact that the wood is in the first stage of rotting does mean that there will occasionally be bits too soft to turn, so it is always a surprise when it turns out well. The softer patch can be see in the early photos on the lathe. As I was cleaning these away I noticed the top edge was fairly decent wood, so the rim kind of formed itself.