the slide rule!
a few years ago, out of the blue, i suddenly remembered the slide rule
(and then promptly forgot it again)
prior to that the thought of one had not crossed my mind in at least two decade
yet as phil points out in his post, this was a device that had been totally part of secondary schooling in maths
then, seemingly overnight, it completely disappeared, wiped itself from cultural memory
i can remember having just got to grips with it to the point of actually getting correct results, and then the first, in those days quite bulky calculators arriving
(imagine being Britain's leading manufacturer of slide rules, and then...)
i wonder what other ubiquitous/totally-established-and-permanent seeming technologies/techniques/artifacts there are that just completely disappeared, like that
possibly slightly too marginal to count, but i remember that hair-singeing was something a lot of barbers offered... it was supposed to prevent split ends... basically like applying an iron to your hair.... as a result barbers often had this unpleasant burnt hair smell lingering
wigs for women?
the pressure cooker?