Three ways could be used to get the first microscopic layer of metal onto
the lacquer.
Silver spray is the newest and trickiest and also the silver pan bath is
still used, similar in its chemistry; it takes longer, and is not as
accurate . Lacquers are treated in a different way, to give metal coatings
at first only a molecule or so thick.
The lacquer surface is sensitized by being dipped into a solution of
stannous chloride which is washed off in a water spray, leaving a very thin
coating. Silver nitrate solution is sprayed at the disk and the black
becomes a mirror of silver in seconds.
The newly silvered disk is washed and moves on to its next treatment. The
next objective is to build up a solid metal backing on the thin silver coat.
This backing is actually being deposited on the front of the original disk.
The original record will eventually be stripped away, leaving the other side
of the silver, the facing down side, as the mold.
