Use the same techniques as with sterling or fine silver-3 parts
water to one part (undiluted) nitric acid. Use any standard resist
technique–there are hundreds of ways to mask the part you don’t want
to etch-electronic supply houses are a good source of many.
After your resist dries well, clean the Argentium piece from finger
oils-I use alcohol, and immerse in tray with diluted acid at room
temperature. Some people heat the solution for faster results.
Agitate gently by rocking the solution over the item every 30 seconds
or so and also tap your tray occasionally to release gas bubbles.
With my concentration of acid, it takes about 10 minutes for a
shallow relief, and about 20 for a moderate deep etch of about 0.8mm.
Note-on deeper etchings, undercutting of delicate patterns results.
Also, there are several other etchants available other than nitric
acid that other folks swear by.