HP 71B cases and the Black Cloud of Death

[Joe Horn]

The original HP-71B case had a thin layer of polyester foam padding between the leatherette outside and the lining inside. That foam is great when it's new, but over time it stiffens, then turns brittle, and eventually disintegrates into black powder. A similar phenomenon destroys loudspeakers whose cone is suspended in the frame of the speaker by a polyester foam "surround". The benefit of this design is that it's lightweight and cheap and very flexible. The downside is that ozone and time make it fall apart.