Overhead projectors are designed to illuminate and ... Since transparencies typically are thin, smooth sheets of acetate film, they have very different characteristics than paper.

Overhead projectors using acetate sheets or rolls were once a common sight in classrooms. Joe Schwarcz writes that it was the sight of one of the machines in a Dumpster that inspired him to ...

Back then, this was a reference to the use of acetate slides on an overhead projector. To me, this always seemed to be a hugely clunky teaching tool – a big machine that tended to make a lot of ...