Etching sterling silver

Jewelry Discussion
1

Hi All, Can someone give me some help with etching sterling silver
with ferric nitrate. The ferric nitrate is no problem, we have a
local supplier here in Los Angeles, who will supply the acid in
powder form. Is it possible to achieve a good etch in say 30 min.
to an hour? How strong should the solution be? Someone mentioned
that 1lb. of acid should be mixed in 1 pint of water, or 7 lbs. per
one gallon of water. After the acid is in solution, can it be
reused? For resist I plan to use Paint Pens, and Press-n-Peel Blue.
All advise will be appreciated.

2 
    Is it possible to achieve a good etch in say 30 min. to an
hour?

Not with ferric nitrate. For this quick of an etch you need to use
nitric acid. The ferrics are used by those wishing fewer health
hazards, but they etch quite a bit more slowly.

    How strong should the solution be? Someone mentioned that 1lb.
of acid should be mixed in 1 pint of water, or 7 lbs. per one
gallon of water.

I use approx. 1 lb. per quart of distilled water, then adjust up or
down accordingly. A more accurate method of measurement is to use a
Baume hydrometer to adjust the solution strength by degrees (similar
to percentage). Different suppliers carry different grades
(strengths) of the ferric. What is a good guideline for one grade
from one supplier may not work for a different supplier.

   After the acid is in solution, can it be reused?

Yes, many times, although you may need to add fresh ferric nitrate
to adjust the strength.

   For resist I plan to use Paint Pens, and Press-n-Peel Blue.

Both will work well, but as a general rule of thumb, don’t use
metallic-based paint pens (silver, gold, copper). These have
aluminum and brass in the composition that can cause a certain degree
of decomposition of the paint pen resist. Only use the regular
colors. Stores that sell models, like car and plane models, also have
chisel-tip paint pens.

3 
        Is it possible to achieve a good etch in say 30 min. to an
hour? 

   Not with ferric nitrate. For this quick of an etch you need to
use nitric acid. The ferrics are used by those wishing fewer health
hazards, but they etch quite a bit more slowly.

they also etch quite a bit more evenly, with significantly less
undercutting. And you can speed it up a whole lot with agitation,
and even more with a low voltage so it’s an electroetch. Spray
etchers using ferric nitrate are fast enough to fit the described
time, though that’s not simple technology any more.

Peter

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