I can tell you from my nitric acid experience that you do not want
to do this. I tried to etch 28 ga sterling with a 1:3 nitric to
water bath. The acid was quite scary when the toxic smoke was
pouring off of it and even though I was working outside and not
breathing around it, I still felt the effects later. An acid resist
will not hold up long enough to etch all the way through your
sheet. I can't even count how many times I kept checking and
repainting my resist. Because my sterling sheet was in the acid
bath for at least an hour, I had also succeeded in getting rid of
all the zinc content in my sterling which resulted in a severely
pitted plate.
OK, first of all, sterling doesn’t contain zinc.
Second, I have been etching silver with nitric acid for years
without seeing any smoke at all. The fumes are nasty, it is true,
so appropriate ventilation and/or mask are important, but it can be
covered with a lid, as well. Your acid may have been too
concentrated. I’m not sure what strength mine is-- I use it as it
comes from Rio.
Last, I have etched all the way through, without any kind of trauma!
When I did it, I made a pattern by photocopying my drawing onto
acetate and ironed the copier ink onto the metal. Before I
transfered it, I flipped it over and made a flopped image on another
sheet of acetate. I had drawn register marks on the original outside
the size of the metal sheet. I put one acetate on each side of the
silver, matching up the register marks, and ironed them on. That
way, I could let the acid work from both sides to the middle. It
took about a half hour, I think, to etch through 28 gauge silver-- I
was actually using fine silver, I think. The two images matched up
almost perfectly, and a little filing was all that was needed.
It is very easy to get pitting on nitric-etched silver, but it has
nothing to do with zinc. Nitric is a vicious devourer of silver, and
will go through the tiniest flaw in your resist. It helps a great
deal if you etch your sheet for one minute before you apply your
resist. This creates a “tooth” for the resist to cling to. Wash and
neutralize the sheet, dry it (no touching!) and apply the resist. If
you use the photocopier transfer method, touch up the image
thoroughly with a paint pen, if you want to avoid pitting. Even a
sharpie pen will help reinforce the resist some.
When I am especially concerned to get a clean etch, I apply a second
copy of the image on top of the first one, matching it up perfectly,
to double the amount of toner that ends up on the silver as resist.
This is painstaking, and usually not necessary-- I’m a bit of a
fussbudget.
I know a lot of people prefer ferric nitrate, but I don’t like it.
You can’t see through it, and, if I remember correctly, it leaves
“smut” (precipitate) on the silver which must be removed frequently
or it stops the etching (I know ferric chloride on copper does that.
Adding citric acid to ferric chlotide is supposed to eliminate the
precipitate, but I haven’t had good luck with it. But that’s a
different issue.)
Anyway, don’t get freaked out about nitric acid, just use it
carefully, don’t breathe it, don’t get it on your skin unless you
like to turn black.
Noel
