Seventy years ago this month, the April 1948 issue of Popular Mechanics introduced a new term to the electronics lexicon, namely the “printed circuit.”

The magazine noted that this truly “wireless” technology was made possible by research by the Bureau of Standards during World War II.  The worker shown above, at Spraywire Laboratories, Inc., of Minneapolis, is making a  board.  It explains that a circuit stencil is applied to a material such as plastic or ceramic, after which a sandblasting process was used to form grooves.  Finally, the grooves were filled with molten metal to form the conductors.