Ah, well I'm guilty! The videos I saw, in the past, were just a ball of fairly fine wire on a plate. This was probably 20 years ago, when I was looking into melting black beach sand in the microwave.
For a rant about that, it turned out pretty neat. I put the beach sand in a thin layer on a dinner plate that was a half wavelength above the bottom of the microwave, turntable removed. The beach sand would start to melt where the standing waves were, but then quickly grow into a wire structure, with the growth of the tips driven by where absorption would be maximized, allowing the thing to heat more, and grow more. I tried to model the resulting "antenna", but none of the open source tools at the time could handle the complexity.
For a rant about that, it turned out pretty neat. I put the beach sand in a thin layer on a dinner plate that was a half wavelength above the bottom of the microwave, turntable removed. The beach sand would start to melt where the standing waves were, but then quickly grow into a wire structure, with the growth of the tips driven by where absorption would be maximized, allowing the thing to heat more, and grow more. I tried to model the resulting "antenna", but none of the open source tools at the time could handle the complexity.