Sanding plaster, that is.
It makes the finest white powder which floats in the air, eventually settling on your clothing, on your skin, in your hair, in your eyes, in your lungs.
full benefit of the all over dusted with talc look.
I dutifully wore the protective gear - a proper thick mask with a vent and safety goggles. These come in 'one size fits nobody'. In order to get the mask to seal adequately and prevent the goggles fogging up when I breathed out I had to tighten it so much the metal nose band hurt. I could move it down a bit, but that just squashed my nose and made breathing difficult. If I loosened it up my breath leaked out the top and under the safety goggles. What with moisture on the inside and plaster dust on the outside, I was removing them every few minutes to wipe them off.
and this was just the first of 4 courses!