Tuesday, 30 August 2011

Etching mother-of-pearl

These last few days, summer has definitely turned into autumn. While the rain and wind makes it dark and cold outdoors, I've been so inspired by my experiments I've almost forgot the boring, chilly weather (though not fully as I have to run outdoors in the rain every now and then -- and it's given me a soar throat). This is what I'm playing around with right now.

The other day, I showed some pics of my accidental brass etching (remember it?). As I like the result so much, I had to do some research online to see if I could learn something more about etching metal with vinegar. As I did that, I stumbled over something else. Apparantly, vinegar is used as an echant when decorating eggs. Patterns are created using bee's wax, which works as a resist, and then the eggs are submerged in vinegar until the outer layer is removed by this mild acid. Particularly effectful when using brown eggs as the vinegar removes the pigmentation in areas not covered with wax.

That had me thinking. Wouldn't it be possible to etch seashells the same way? Pearls, seashells, egg shells -- they all contain some sort of calcium compound, which makes them porous and sensitive to acids. And we all know about Cleopatra dissolving a pearl (i.e. nacre, mother of pearl) in vinegar to create the most expensive drink in history. I have to try this, I thought while mentally going through my bead stash looking for something -- anything -- made from mother of pearl.

As I didn't have any info specifically on vinegar etching MOP, it was truly an experiment. I'm sure there are others that have done this and written about it online, but I didn't have any how-tos available at the time (in fact, it probably didn't occur to me to google "etching seashell with vinegar"). So I had to figure things out myself. I didn't know how long to let the shell soak in the vinegar or what other types of resists I could use, which would withstand the effects of the vinegar without damaging the MOP (either when applying or removing it). For my first piece, I simple dripped a few drops of wax onto a MOP bead and submerged it in the apple cider vinegar. Eagerly waiting for a result, I got tired as it took much longer than the recommended times for etching eggshell -- and forgot about it for a couple of hours. When I finally got it out, the vinegar had created a nice, deep etch (se photo above, bead on left side).

I went on to try another resist: white glue, which works with etching liquid for glass (I've used it here). Unfortunatly, the vinegar dissolved the glue -- not sure if I should've let it cure longer or if it'd still be as unsuccessful -- before I could get a good etch. All I got was a nice matte surface (photo above, pendant in middle).

Next experiment was a flop. I don't even have a photo of it. My plan was to do something similar to what you can do when etching on metal: cover the surface with resist and scratch a pattern in it. That would leave a shiny background and an etch-out (matte) pattern. Sounded fab, but maybe I applied the wax too thickly (dripping onto the bead rather than being brushed on) or maybe the wax was too hard: scratching a pattern with my needle, I maybe caused the wax to separate from the surface, leaving room for the vinegar to seep in. Maybe if I'm more careful, it'll work. This time it didn't.

I then when on with another method I've used for glass and stone etching: using peel-off stickers as resists/masks. This was much, much more successful (se butterfly bead above).

So far I'd used dyed shell -- mainly because that's what I had and that's what I was prepared to sacrifice. I went on to etching a few small white MOP mosaic tiles. Etching on white MOP has a big drawback, I discovered: it's really hard to see the motifs. There's not much contrast between the etched and the protected areas. The latter is more shiny, but there's still a pearlescent effect visible in the etched areas so that you must hold the piece at an angle to see the pattern. Just look at the pics below.

What to do? It might be a nice, subtle effect, but I want the motifs visible! On a whim, I took out the only dye I have: alcohol inks. What would happen if I wiped the surface with the ink? Surely the etched areas are more porous than the polished areas protected by the resist, meaning the ink would soak into those areas faster -- thus leaving the pattern in a different colour/hue?

It worked! Not perfect -- not by a long shot -- but for a first try I'm satisfied with the result. So all I have to figure out now is the best way to dye the shell: what dyes to use (e.g. egg dyes?), how long I can soak the shell before the contrast disappears etc.

And then, of cause, I have to come up with a more exact time for how long to I should etch the shell for the perfect result. Because I don't know that yet. All these pieces have been etched a minimum of one hour, but most of them were etched a least two hours, the first piece being etched the longest.


  1. Very good trial and error. I've played around with this idea but never thought to use alcohol inks. I love your results!

  2. Thanks!

    As for the ink, I thought some more about that yesterday. First, I began thinking about adding dye to the etch bath, but then I thought I might be overthinking it. Maybe I should just dye the shell, with sticker or other resist instead of first etching it. A little vinegar to make the surface more porous and thus accepting the dye more readily, yes, but first a long etch bath and then a dye... I don't know, it might be overkill. It's nice with the slight relief and maybe that can keep the motif from being dyed too, but it might be an unnecessary step.

  3. OH MY! This is the first blog I am visiting today and I have to say that I am mighty impressed! I love that you just attacked this problem, like a science experiment, with trial and error and all sorts of information gathered and gleaned! This is delightful! I have some big MOP shell things like this, and I might have to try this. Alcohol inks I thought of too, but they can be tricky. I use a small paint brush to get into precise places. Maybe a littl bit if it just outlining the etch would give it more of an antiqued look. Or what about paint? That way you could wipe it off and have the details highlighted. This is genius, and I thank you for sharing it with me! I am off to read your other posts about etching!
    Enjoy the day!

  4. Ah, yes... I've spent most of my life in school and at uni so I guess I'm just very used to approaching all problems in a very analytical way. Some might find it a bit too serious sometimes, but when trying new things I think you must try and be at least a tad scientific -- e.g. just changing one parameter at the time -- if you want to be able to repeat the good results in the future. Some might, as I mentioned, find it boring and too rigid, but I like this approach to problem-solving. Science is fun.

    And thanks for the suggestions! I like the idea of paint to hightlight the reliefs. I think it might be especially useful for the pieces that are more deeply etched. I will have to try that! I don't have much dye, but I do have acrylic paints.

    I was rummaging through the cabinets yesterday in search for some tea so I could test tea dyeing the MOP. Didn't find any -- no one in the family drinks tea, but we sometimes have a few bags for when tea-drinking relatives drop in -- but today mom had bought some for me.

    It seems like I'll soon have a third post to write on the subject. Let's just hope I can test it all before running out of MOP (which I'll do soon)! *lol*


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