Hi everyone! I've been reading the post for some time and I have a question too. Has anyone ever made anything with copper inlay? How exactly would copper act in cone 6 glaze firing? I would greatly appreciate your advice or even a reference to where I can find more information on a subject. Thanks, Veronika
I have used copper in pit fires which are really low temperature and the copper just burns away. The oriental pieces that looked like they had gold inlay repairing broken pottery were actually done with lacquer (hazardous to the health as it turned out). I think if this is what you want, you would fire the piece first to cone 6 and then do a low fire enamel technique... Just a guess mind you.
Copper won't survive at cone 6. It melts at 1984F (1084C), which is roughly cone 03, but it oxidizes like crazy long before that. If you were making flat tiles, you *might* be able to get it up to melting by covering it with a protective flux, but I imagine this would take some amount of experimentation to get working.
This seems to be generally true of all common metals in oxidizing atmospheres... they oxidize long before they get to melting. I don't know if you could get decent melting in a fuel kiln fired in reduction, but I bet it wouldn't be easy... you'd have to keep it in reduction throughout the whole firing cycle.
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
In message , Bob Masta writes
This is a question I've often wondered about for many years and never got around to asking. Glad it's turned up now. Given that the copper oxidises long before melting, would it leave sufficient traces of oxide at lower earthenware temperatures when it could, maybe, be used as glaze colourant as part of design. Would it always produce copper oxide, or would that depend on kiln atmosphere? Can any other metals be used in this sort of way? Hope you can follow my thinking - I have a bad cold and a fuddled brain. Thanks
Susie
I only have personal experience with oxidizing (electric) kilns. I think you could probably get this to work, and it might make an interesting effect, at least for non-functional ware. The copper or iron (steel) that I've fired invariably oxidize to black, but I haven't put them next to a glaze. I'd expect the oxides to bleed into the glaze at the edges of the original metal, perhaps giving a green halo around the black copper oxide lump. Might be fun to experiment with different base glazes to see which promotes the most bleeding.
If you covered the metal with the glaze application, it should reduce the oxidation when the glaze becomes fluid enough to block oxygen from getting to the metal. So there may be some interesting effects with different thicknesses, as well as different glaze melting temperatures. Try flat tiles at first, so you can over-fire the glaze and not worry about it running off the piece.
And please report back with your results!
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
In message , Bob Masta writes
Hi Bob
I don't make anything useful at all, so no problem there. I'm not working at the moment but will give this a go when I get going again. There may also be some ironstone clay which I can dig out of the ground on a friend's farm, so that's going to be something to play around with. What might the firing range of ironstone be?
Thanks for your thoughts.
Susie, Isle of Arran, Scotland
In message , The Splanns writes
I had some success a few years ago with the application of very fine copper wire in semi-random patterns on to a white glaze.
I needed very fine wire: I would guess about 36 swg. I got this by stripping strands out of some extra-flexible cable as used for testgear leads.
Spray the glaze; when dry, stick the wire on using CMC to help it stay in place. Fire to cone 7. The copper migrates to give interesting green trails.
If I knew how to do it, I'd put an image up, but I understand that simply attaching one is frowned upon.
Jake Loddington,POULTON-LE-FYLDE, Lancashire, U.K.
i have experience with copper during glass fusing, around the 1500F temp range. if you coat copper with a clear ferro glaze or a borax film, you'll tend to have shiny copper in that range. uncoated, you can get anything from black to green to pink, depending upon how much O2 gets to it when it's heating. if you can isolate it from O2, you tend to get more coppery colors.
regards, charlie
Susie, I don't know about the firing range of ironstone clay. Is it soft and plastic, like normal clay? Or full of grit? A lot depends on the "clay" part, as far as firing range goes.
With the local clays around here (Ann Arbor, Michigan, USA) I find that they would make decent low-fire bodies, except they tend to be full of lime bits that cause the infamous "lime pops" after firing. They can be sieved out, but that's a lot of work for body clay, which you use a lot of. On the other hand, they make *wonderful* brown glazes at cone 6, and sieving that smaller amount is no big deal... especially since I tend to sieve most glazes anyway.
The color is typically "bean-pot brown" and I think this clay must be pretty close to Albany slip.
Anyway, assuming that you are mostly interested in using the ironstone clay as a glaze, I'd suggest sieving at 80-100 mesh and applying it as a glaze over bisqued stoneware test tile. Then fire at your desired target cone and see how it looks. Based on my experience, cone 6 would be a good choice... but the ironstone may have other ideas.
If the tile looks like it got really runny, and you still want to use it at that cone, try glazing simple test pieces with catchers under then in case the glaze runs off. If it's too runny, you can try adding kaolin (or your regular body clay, sieved).
In the unlikely circumstance that the glaze didn't melt at cone 6, you might have a suitable body clay. Just remember that digging and processing enough clay for much body use can be a real chore. And if you are going to cover it up with glazes anyway, there's not much point except sentimental reasons (which are fine, but only go so far). But a glaze clay not only goes farther for less effort, it is also visible on the outside of the piece and works great for sentimental purposes as well.
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
O' course you could always once fire it (if it's got lime) get it above cone 6 and the lime melts and forms part of the body, that's why Stoneware (once fired) never suffers from the dreaded white pits... Hugs Eddie
The local clay is like Albany Slip or any other low-fire clay: It is completely melted at cone 6. So yes, the lime is part of the body, but the body is a puddle! But it's probably true that I could use it as a glaze without sieving out the lime, and the lime would simply add to the glaze. However, the sieve also removes sand and other inclusions that don't melt as readily and leave a gritty glaze surface.
Best regards,
Bob Masta DAQARTA v3.50 Data AcQuisition And Real-Time Analysis
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