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?
indefinitely…if your radio shack solution becomes concentrated
before the bottle is opened top it with distilled water to the
original volume.
after opening and one use, mark a line with a sharpie or permanent
marker to indicate the level when storing and then top that off with
deistilled water before use.
if it has crystallised place the open bottle in a sunny and level
position ans add wae to it.after it is thoroughly warmed, or hot
recap, shake vigorously and it should dissolve again…
Nitrates break down in sunshine so should be made up when needed.
They will keep in a darkened environment almost indefinitely though.
I would recommend using all your solutions within a fortnight of
making them but they will keep longer than that if stored in an
airtight container away from heat and light. Make up as little as you
can and then you can afford to dispose of them afterwards.