Dust pucks
Question: I have a coal-fired Aga cooker. It is refuelled by tipping coal
into a small hole in the middle of the hotplate. During refuelling with wet
coal, water droplets fall onto the hotplate and bounce around violently,
scattering as they boil and superheat on contact with the plate. But some larger
droplets gather a layer of dust on their surfaces (which I suspect comes from
coal that has also landed on the plate).
The surprising thing about the coated droplets is that they stop bouncing
around and form neat, squashed-sphere shapes, 3 to 4 millimetres in…
