Long before the days of Health & Safety In The Workplace,
I worked in the research dept attached to a power station
and we used to boil the FC solution in a saucepan on the
little mains cooker that we had.

Insofar as the saucepan was aluminium (aluminum to the
non-English-speaking Yanks), I am surprise that there was
any "strength" left in the solution to etch the copper!

(Having made the mistake of using an aluminium stirrer in
my own etchings!)

"Bob Liesenfeld" wrote in message
...
I suppose most of us know that warmed etchant works faster than
room temperature juice.