In an interesting reminder that physics is always at play in pottery, the bird necks twisted clockwise during firing. Given that the wheel was spinning counter-clockwise, the frictional force utilized to narrow the necks was clockwise--meaning the necks twisted further when fired, rather than untwisting. Someone told me years ago that teapot spouts can untwist when fired, so here's proof that that's actually a myth: they twist more, not less. (I get around the issue with teapot spouts by pulling the spouts in rather than collaring them in, but heron necks are a little too long for that.)
