I also got an offline response discussing the strenght of my
ferric nitrate (500 grams to 1 pint water) being too strong.
Sharon, if you’re really going to do a bunch of etching, it will pay
you to invest in a Baume’ hydrometer that measures specific gravity,
in the range of 15-60 degrees. Different grades of ferric nitrate, as
well as different manufacturers, will not be equal in the strength of
the ferric nitrate by volume or weight. You want a stronger solution
that bites fast and deep for fine lines. You want a weaker solution
for a slower bite in areas that have lots of open (negative) spaces.
Also be sure to use distilled water to make your solution, as regular
tap water contains contaminants (iron, lime, calcium) that will
affect your etching results.