I've found lots of good about etching and etchants
online, but very little about the shelf life of the chemicals. I am
using ferric chloride (bottled liquid from Radio Shack) to etch
copper and brass, and ferric nitrate (purchased dry crystals to
dissolve in water) to etch silver.
If I only do etching once or twice a year or so, how long will the
chemicals remain fresh, viable, and useful? What if I have some old
ferric chloride that's been sealed but sitting in a cabinet for
several years? Still any good? If I mix up the ferric nitrate, must
it be used right away?
Thanks for your advice.