JW wrote:Are you still getting these?
I vaguely recall that I got a few last winter. It's too warm still this year to have had any chance.
Similar examples are not uncommon in the mineral and materials science world. They usually grow from the base, as material is rejected from the matrix, older material is pushed upwards, forming spikes, curly-cue's, columns, etc... I imagine that water in the wood freezes and expands, and so is forced outward at specific points (pores?) in the wood, and so forming spikes.
Having read some around Linden.g's travails and the background science of trying to grow snowflakes, I'm inclined to think that these form like frost, by direct crystalization from vapor. There's clearly something special about the wood to get them started, but I don't think the water is actually coming from the wood in the sense of growing at the base and pushing the spike outwards. These things are perfectly straight, spiky, clean, and much larger than pores in the wood. (See the other threads linked from the first post here.) It's very different from the "extruded" appearance of
some other ice that I know was formed in the way you're describing.
I guess catching a time lapse of them growing would tell for sure. Maybe if they start forming regularly this winter I'll give that a shot.
--Rik