Saturday, January 16, 2010

Experimenting with Etching

In the past nine-and-a-half months since Sawyer was born I haven't had much time to make production jewelry, let alone experiment. The little time I am able to get I usually work on class development and making samples. One new class Sonja at Sticks & Stones in Mankato wanted to be able to offer was etching.

The Bead Monkey, here in the Twin Cities, is also offering etching but, as I understand, they are using Ferric Chloride. This is a great mordant, but only lasts so long and, as with all etchants, needs to be treated as hazardous waste when it's spent. It's also a very dark solution, so you can't see what's happening as the etchant works on the metal. So, for those reasons I started working, instead, with a seed batch of hydrochloric acid and hydrogen peroxide, which after etching a couple of copper pieces turns into the reusable, refreshable cupric chloride. Cupric chloride is a mordant for copper and brass, and I still need to see if it has any effect on sterling silver whatsoever, but for the very low cost, lack of trips to the hazardous waste facility, transparency of solution, and effectiveness, I really like this stuff so far.

When you mix a new batch of hydrochloric acid and hydrogen peroxide (in a 3:1 ratio, done in a pyrex mixing cup -- a different brand than the kind you might have in your kitchen to prevent accidental switching) the bite it has on the metal is quite fast and deep. Very nice. I've started to notice, now that my solution has turned into the cupric chloride, that the bite isn't as deep. The result isn't necessarily bad. After about 20 minutes, running my fingers over the metal, I can't feel a textural difference, but there is a visual difference. The non-etched metal that was covered by the resist is very shiny, but the etched portion is matte. I think it's a very nice effect. Now, I've left a piece in the solution for the night. We'll see the wisdom and result of this in the morning.

The resist I used in this case I was using DecoColor opaque paint markers in white and black ... both work the same but the white cleans up better. Both require turpentine. When the solution was fresh (HCl and H2O2), I tried using red and brown Sharpie markers. The ink tended to disappear over time, particularly if I didn't go over the lines more than once, but what I had originally drawn was clear in the etch and the gradual removal of the ink may just have been due to the strength of the acid. I still need to try the DecoColor pens with in the fresh solution. I suspect it will be more durable than the Sharpie drawings, but I don't yet know if it will totally resist the mordant or not. I've also purchased some asphaltum (and Ferric Chloride, for that matter) with which I can do some sgrafitto, but the downside is that you need Naphtha to remove the asphaltum when you're done and it seems a little silly to buy Naphtha for just that one application, whereas I use turpentine - needed to remove the paint from the paint markers - for other things, too.

We'll see what we have tomorrow. I'll also edit this post then and upload some photos. Yay!