Thursday, May 14, 2009

More On Bronze

WARNING! Even more technical content than yesterday. But it's my blog and my little record and I know some of you are fascinated with science. OK maybe not, but you tolerate my dalliance.

These are the bronze clay pieces I fired yesterday, all cleaned of carbon, and shined up with a wire brush. What I didn't mention was that these were fired in coal based activated charcoal. In the literature (which is actually scanty) the patina you get with this firing medium is unpredictable, partly because of the mineral impurities in the medium. I actually suspect it is a combination of both the reduction firing and the impurities. This reminds me a lot of the flashing you can get on raku with copper glazes/washes when you apply post fire reduction. Given that bronze alloy has a large component (majority) of copper this makes sense. At least to me.

I'm liking the surface of these pieces now. They have a sense of antiquity, of old coins. And unlike raku they have a permanence. How long? Don't know. These are definitely a time will tell thing. There really is that little experience with the long term stability of surfaces in this kind of work. I do know that really vigorous, really rough wire brushing does not remove the patina and does not scratch the surface. This stuff is tough!

One of the pieces I made was a tiny little disk, purely for potential experimentation with etching. I cleaned the piece up, used a marker to apply a resist. Then suspended it in 'Etchant' for 30 minutes. (I have 1 of 8 bottles still on the shelves of Radio Shack as of 3 weeks ago here in my small community). Nice job of stripping away the patina! And the resist. Nothing.
I really, really wanted to see what it might look like to contrast that dark patina with fresh raw bronze. So I flipped it over and used acrylic paint. Thickly applied acrylic paint left to cure. Well I got etching, but it seems that it eats under the patina surface. The surface just peels off. Oh well. More experiments, maybe? Any ideas out there?

Just one last little note. Even though I fired these pieces as best I could with the standard firing schedule. I think they are just a wee bit over fired. There is just the tiniest bit of pitting in the surface and a wee bit loss of detail. They are fully sintered (fused together) but a little overdone I think. Kind of like cookies that get a bit tough because you've over baked them by 2 minutes.
Off to the porcelain tomorrow. But more development of this in the works!
Cheers, LeAnn


sharon said...

LeAnn, I truly do not understand a lot of what your doing, BUT, I do know that I still like these pcs, I like "Crusty"!! When you said that word I immediately was intrigued! I like pits, holes, ancient, worn, archaic, primitive, aged, craggly, gnarly, and your pcs!! Overdone, underdone, half finished, bits and pcs... these are things I like. I have no doubt you will succeed in your endeavors here.

SummersStudio said...

Hey there Sharon. Thanks for letting me have my little escape into the technical side. A lot of what I do has got that side of it. More than anything, I think this new stuff is going to have a lot of 'crusty' to it. So I'm glad you like that!

stregata said...

love these! And love the technical side!
I have also found permanant markers and ink not quite sufficient. It works sometimes, but best on a very smooth surface that must be absolutely free of anything remotely fatty (such as fingerprints). I'm thinking the pitted surface is allowing the etchant to creep underneath the resist. I have a substance that artists use to coat copper plates that will be etched and used for printing. I will e-mail you, this is getting too long for a comment.

2ifbysea said...

Hey Leann! As a resist you could try Asphaltum (not sure of the spelling). It's what enamelists use as a resist.

LLYYNN - Lynn Davis said...

LeAnn, When I have experimented with etching brass and patina, I etch first and patina afterward. In copper, even stamping into it will sometimes dislodge the patina. As I understand it, the patina rests on the surface, where the metal has oxidized and interacted with the air, so it makes sense that etching the surface would remove it. Have you experimented with liver of sulphur after firing, I know there's a high percentage of copper in the bronze, you may be able to get interesting results with LOS in a cool solution.

Thanks much for sharing the process. The research and development phase is very interesting, isn't it?

SummersStudio said...

Renate and Cristi, thanks for the information on resist. I may take this further on these pieces.

Lynn, I love the development phase almost as much the final outcome. It is what keeps me working with this or ceramics for that matter. There is always something new to do!

On the patina, unlike los patina, the flash from the firing is quite deep and well bonded to the surface of the bronze but not completly adhered. It will be interesting to see what happens over time. And I'll keep working with it.

Marie Cramp said...

Love it, I honestly have not ever seen anything like it. I have never used ceramic in my jewellery making, but then again I only started in january. I will just have to check out your ETSY.
BTW I am linking you, so I hope you check me out.


SummersStudio said...

Welcome Marie and thanks! I will check out your blog.

Anonymous said...

Great info, keep it coming.

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Anonymous said...

I love these they look like ancient treasures

Andrew Thornton said...

Hey! So, there's a couple of steps where there might be issues. For one, your resists might be too weak. Try a hard ground, like stregata suggested. We used it when we used to do intaglio printing. Also try nail polish. This can be removed with acetone and works well. Also, there's blue photo transfer papers that work nicely as well and can achieve repeatable patterns.

Also, your etching mordant might not be strong enough or not interact with the metal properly. You can get copper etchant from Metalliferous.

Also try cleaning the pieces with rubbing alcohol and allowing them to dry before etching. This will insure that any oils from your hands is cleaned off.