Do you need to neutralize it with anything after you're done etching?
I rinse the piece thoroughly in warm soapy water. The reaction
between ferric nitrate and silver is slow and steady, not
carnivorous they way nitric acid is. When I have the depth I
want, I rinse the piece, remove the resist [more on that later],
and scrub the whole thing with an old toothbrush and a sloppy
paste of baking soda.
What concentrations do you use? (I'm assuming it comes as a dry salt.)
It comes as a dry salt and as a liquid. I highly recommend the
dry salt over the liquid since the liquid does have a shelf life
[not a short one, but it does fade with time]. I mix enough dry
salt into distilled water to make it look like good coffee [with
a yellow tinge…bleh]. Use a high quality tupperware-type
container with a lid that seals tightly. Work in an area that
will contain all spills; ferric nitrate has the odd
characteristic that it doesn’t seem to “dry” – little splatters
stay wet and kind of sticky for a long, long, time. And they
stain like the dickens. It might be worth a glace at Oppi
Untract’s big jewelry technologies book to see if he gives an
exact amount to mix with water. If you don’t have the book, just
holler…
If you don’t use an anodizer, how long can you expect to leave
silver in the etch bath for a significant etch? (Textural, not just visual.)
Since I didn’t use an exact formula to mix my bath, I won’t get
the same results that you will. Always do test strips – and if
you’re using the bath heavily, do one every now and then to see
if the solution is becoming exhausted. This is also a great way
to test different resists. Start out with the entire strip
covered [see diagram below] and etch for 30 minutes. Remove some
resist and etch for 15-20 minutes more, having brushed off the
sludge with a feather. Pull it out and remove more resist, and
put it in for another 15-20 minutes. Keep this up, with a
careful record of your times until you get the depths you want.
It can take up to four hours, with periodic gentle brushing, to
get a really deep etch. But it will be a clean etch, with
little undercutting and a very uniform result. Great for detail
work. Try this pattern for your test strips:
| resist |
|_______________________________________|
| |
| area used for test |
|_______________________________________|
| resist |
|_______________________________________|
Be sure to cover the edges and back. I use a permanent paint
marker for the edges and well-burnished-down contact paper for
the back. By leaving some resist on the sides and doing your
test down the middle, you will get a sense of how much
undercutting will/won’t happen over time.
Agitating the bath will noticably speed the etch, since it
shakes the sludge off and mixes air into the reaction. Get a
cheap little bubbler motor from your local pet store and a length
of air tubing. Punch a hole in the top of the tupperware near
one corner [the old hot nail technique – smelly but effective]
that will allow the air tube to enter the bath. Suspend your
piece etch-side-down and run the air line in under it [not in
contact, but nearby]. Snap the lid on, plug in the pump, and let
it burble away. The lid will intercept the fine spray from
popping bubbles.
A few notes on resists:
-
Daniel Smith Artists Supplies in Seattle WA carries a wide
range of resists for etchers. Some of these come in forms that
cost more to ship because they contain flammable solvents; others
can be purchased in ball or lump form, ready for you to mix at
home – a lot cheaper and easier to store. I use hard ground,
stop-out varnish [used to touch up leaks in hard ground], and
rosin. Buy the rosin in lumps, then grind it up in a mortar and
pestle. Sift the crushed stuff through a couple of gradations of
screen or cloth to get different sizes of particle. You then
sprinkle or sift the particle onto your squeaky clean metal and
GENTLY [like with a distant Bic lighter] heat the metal until
the little fragments melt and adhere to the metal. By using
gradations of large to small particles, it is possible to get
stunning textural transitions on a piece. I enamel over the
resulting etch, then stone back to the original level of the
metal, giving a fabulous color effect either by itself or under a
transparent color.
-
Remove resists with the least toxic solvent possible. To my
considerable delight, the commercial cleaner “Goo Gone” works
perfectly on every single resist I use. Orange oil in its pure
form works faster, but it will irritate your skin and can be hard
to find at a reasonable price. Goo Gone uses orange oil as its
active ingredient, but its gentler on the skin, easy to get, and
cheap. No more mineral spirits in this house! Be sure and use a
good detergent [e.g. Dawn] after the Goo Gone has taken all the
resist off, since it will leave an oily film [and a lovely citrus
smell] that must be removed.
Let us know how it goes!
Anne Hollerbach
@alhollerbach