Nitric acid etching of silver jewelry

A. Hi William. Although a stoicheometric estimate of how much baking soda is required could possibly be attempted, the practical answer is that you can't add it all at once anyway, excess baking soda isn't going to hurt anything, and the neutralization has to be done agonizingly slowly because of the foam and fumes it will generate, so just keep adding it until there is no longer any evidence of hydrogen gas evolving :-)

Luck & Regards,


Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

A. I have done some silver etching. It's very different than ferric chloride ⇦this on eBay or Amazon [affil links] and a very big step "up". But, the results are very nice and you can get just as clean an etch in the silver as you can with the ferric chloride ⇦this on eBay or Amazon [affil links] .

The nitric acid is 1 part to 3 parts water .... remember: add acid to water. I am told (we used premix in the class) that if you add the nitric to the water too fast, an explosion is possible. Wear goggles ⇦this on eBay or Amazon [affil links] and all your other protective gear if you choose to make your own solution and do it under a hood. Unlike ferric chloride ⇦this on eBay or Amazon [affil links] , nitric acid is nasty stuff. Premix is available at Rio - and there is a hazmat charge for shipping.

We used a 12-volt battery and titanium wire in a glass dish. Attach a titanium wire to a sheet of titanium (about 22 or 24 ga) that is about the size of your piece and the other end to the positive terminal. Curl the other wire a bit so that you can put your silver piece on top of it. Attach the other end of the wire to the negative battery terminal.

Submerge the titanium sheet and the wire coil in the nitric acid (glass dish). Place your silver piece on the coil. Bubbles form on top of your piece as the etching takes place. They interfere with the etching and must be gently brushed away. We used cheap artist's brushes with no metal (do not use any metals in this solution other than the titanium). When the nitric melted the bristles too much we changed to a new brush. If I remember right, fresh solution gave us a good etch in about 15 to 20 minutes.

Good luck with your etching.

A. Nitric acid attacks silver. Adhesive vinyl or wax resist nitric very well.

A. Hi, Valerie. Nitric acid can be diluted, then mixed with baking soda [in bulk on eBay or Amazon [affil links] until litmus paper (pH paper) says the solution is neutral. Safety issues and environmentally responsible disposal are topics rather large to be dispatched with in a public forum though. I would suggest that you start with the EPA website and search it for appropriate terms. The EPA writes volume 40 of the Code of Federal Regulations, so you can often find those regulations by including "40CFR" in your string of search terms. Good luck.

Regards,

----
Ed. note: Hi Ari. We appended your inquiry to a thread where Cheryl B has already answered it. Good luck. But get back to us if you need clarification.

A. I've used nitric at higher strengths, usually y 1-2, for years.
The resist I've found most useful is a roofing spray asphalt. I've sprayed several thin layers to cover the whole piece.
I make sure my sterling is absolutely clean so the resist can stick to it.
It's a pretty thin layer and the acid doesn't creep under it so much.
I can achieve very fine lines with it; maybe not too deep, but deep enough.
I never throw my mordant away because I can use it for later etching if I just add a few drops of fresh acid to it. And it's great for a bright dip.
Why throw it away?
I've never brushed the bubbles off either. I did today. Let's see what happens. I hope it didn't loosen the resist. The resist getting brittle is the thing to watch, IMO.
If you'll note, the bubbles form and then disperse, so the acid is still working.
I'm sure a lot of jeweler's have more experience with this technique than I do, but this works for me.
That roofing asphalt spray is the key.
Good luck to us all!

A. You might want to use Ferric Nitrate instead of nitric acid for etching silver. It is much safer and easier to use. Use just like you'd use ferric chloride ⇦this on eBay or Amazon [affil links] if etching copper.