A book has just fallen down the side of a filing cabinet in the bedroom - the cabinet has been there for some 20 years, and it became clear as I poked with a long stick to get the book out of the narrow gap that a lot of grey almost felt like material had accumulated, some of it lumps of 100mm x 50.
What actually is this and why does it clump together ? Yes I know it's dirt/dust - call it what you like but what's the mechanism that makes it bind ?
Rob