AWPottery Posted February 9, 2014 Report Share Posted February 9, 2014 I was recently browsing pictures of raku pots and saw some done by a potter named Tim Scull. He inlayed copper wire in the pots. I liked the concept and effects that he got from it. What I was wondering is 1) at what stage do you think he inlayed the copper wire? (during the greenware state and fired it on the pot or after glazing it and just wrapping it around the pot when rakued? Anyone have any thoughts or ideas? 2) Does copper wire give some type of green colored effect on the pot? b/c I noticed were he wrapped the wire there was green near it. Anyone know at what temp copper wire melts? I guess it doesn't get completely hot enough to completely melt the wire when rakued? Thank, Amanda Link to comment Share on other sites More sharing options...
Tyler Miller Posted February 9, 2014 Report Share Posted February 9, 2014 Amanda, I had to google Tim Scull's work. It's beautiful! This is just a guess, but I would imagine the wire would be applied after bisquit firing, to avoid complications associated with shrinkage, then possibly before applying glaze, possibly after, but before seems like far less of a headache. To answer your second question, the copper absolutely gives coloured effects to the pot. The glaze acts as a flux in the metallurgical sense, picking up the oxides coming off the copper. I have some crucibles with the very same greens on them where the borax welded itself into the vessel wall. Copper melts around 1975 F, but flows above 2000 F--when I've tossed orton cones in my furnace alongside my copper melts for casting, it winds up flowing around cone 3-4. As an aside, stay away from silver-based flashes if using copper like this. Silver nitrate/carbonate/oxide, will reduce to form a eutectic with your copper wire and it will lower the wire's melting temperature significantly. Link to comment Share on other sites More sharing options...
Norm Stuart Posted February 9, 2014 Report Share Posted February 9, 2014 I suspect this paper could be very helpful. It details the oxidation behavior of copper between 660 F and a little bit hotter than Cone 03. http://aml.jlu.edu.cn/Htdocs/bd/jq/article/MMTA061.pdf Once the copper is inside a reduction raku firing, it will not be prone to this oxidative effect. Amanda, I had to google Tim Scull's work. It's beautiful! This is just a guess, but I would imagine the wire would be applied after bisquit firing, to avoid complications associated with shrinkage, then possibly before applying glaze, possibly after, but before seems like far less of a headache. To answer your second question, the copper absolutely gives coloured effects to the pot. The glaze acts as a flux in the metallurgical sense, picking up the oxides coming off the copper. I have some crucibles with the very same greens on them where the borax welded itself into the vessel wall. Copper melts around 1975 F, but flows above 2000 F--when I've tossed orton cones in my furnace alongside my copper melts for casting, it winds up flowing around cone 3-4. As an aside, stay away from silver-based flashes if using copper like this. Silver nitrate/carbonate/oxide, will reduce to form a eutectic with your copper wire and it will lower the wire's melting temperature significantly. Link to comment Share on other sites More sharing options...
Tyler Miller Posted February 9, 2014 Report Share Posted February 9, 2014 Cool paper, Norm! This actually has applications to some aspects of a project I'm working on right now, so I'm really glad you posted it. I definitely forgot to add that oxidation only happens in an oxidizing atmosphere. I've never had problems getting copper to form oxides, only trying to keep them from forming. Heating a piece up in any atmosphere, pulling it, and air cooling it would do the job nicely. I was under the impression Scull's work was done that way and not put through reduction. I wonder if there's a way to get the red oxide to form, as well. Link to comment Share on other sites More sharing options...
docweathers Posted February 9, 2014 Report Share Posted February 9, 2014 can someone summarize with that paper says that's relevant to glazing in five sentences or less? Link to comment Share on other sites More sharing options...
Norm Stuart Posted February 9, 2014 Report Share Posted February 9, 2014 What the paper says is copper will oxidize completely if fired in a bisque. The copper filaments on his pots are melted and partially, but completely oxidized. So based on the paper I assume Tim Scull drops these copper filaments onto pots just before the reduction part of a raku firing. can someone summarize with that paper says that's relevant to glazing in five sentences or less? Link to comment Share on other sites More sharing options...
Tyler Miller Posted February 9, 2014 Report Share Posted February 9, 2014 Norm, I didn't take that from the paper at all. I thought it was simply about activation energies and CuO/Cu2O oxide scale formation. That is, I thought it was a study of why copper scales heavily in an intermediate temperature range and the rates of change in scaling. The word complete doesn't occur once in the article, at any rate. It definitely won't oxidize completely in a bisque. I've got a lump of copper in my hand right now from a failed water casting I did this past summer. I had trouble getting the furnace up to temp and burned off all the charcoal keeping the oxygen out of the crucible. I got a partial pour because of the temperature problems and the rest of the copper went back into the furnace, where it sat at well above bisque temp and cooled for hours. The borax/glass keeping things clean and sealed had been poured out with the copper that made it to the water. The lump's got a heavy coat of red and black scale on it, and likely a number of bubbles in the centre, but it's definitely still metallic copper. Link to comment Share on other sites More sharing options...
Norm Stuart Posted February 9, 2014 Report Share Posted February 9, 2014 You're an excellent reader and I like your management summary better than mine. Activation energy is very similar to cone heat-work, and larger pieces of copper are protected from further oxidation to a degree by their oxidative covering from further oxidation. I based my summary for ceramic firing on the artists use of the word copper filaments which would oxidze when placed and partially reduce back to a metal form in the reduction chamber. Use something thicker than a copper filament and the answer is more complex. Norm, I didn't take that from the paper at all. I thought it was simply about activation energies and CuO/Cu2O oxide scale formation. That is, I thought it was a study of why copper scales heavily in an intermediate temperature range and the rates of change in scaling. The word complete doesn't occur once in the article, at any rate. It definitely won't oxidize completely in a bisque. I've got a lump of copper in my hand right now from a failed water casting I did this past summer. I had trouble getting the furnace up to temp and burned off all the charcoal keeping the oxygen out of the crucible. I got a partial pour because of the temperature problems and the rest of the copper went back into the furnace, where it sat at well above bisque temp and cooled for hours. The borax/glass keeping things clean and sealed had been poured out with the copper that made it to the water. The lump's got a heavy coat of red and black scale on it, and likely a number of bubbles in the centre, but it's definitely still metallic copper. coppernugget.JPG Link to comment Share on other sites More sharing options...
Mudslinger Ceramics Posted February 9, 2014 Report Share Posted February 9, 2014 I was recently browsing pictures of raku pots and saw some done by a potter named Tim Scull. He inlayed copper wire in the pots. I liked the concept and effects that he got from it. What I was wondering is 1) at what stage do you think he inlayed the copper wire? (during the greenware state and fired it on the pot or after glazing it and just wrapping it around the pot when rakued? Anyone have any thoughts or ideas? 2) Does copper wire give some type of green colored effect on the pot? b/c I noticed were he wrapped the wire there was green near it. Anyone know at what temp copper wire melts? I guess it doesn't get completely hot enough to completely melt the wire when rakued? Thank, Amanda Hi Amanda Copper wire melts at 1083C, the copper was laid onto the glaze layer- it gives the green melt trails coming down the pot's sides as the glaze moves in the firing Have tried copper in firings at uni....(spent my entire undergrad experimenting!) .....on a dry clay body copper wire will give a black crusty partially disintergrated line, put it into a borax or lead based glaze and it will give green just as copper carb or oxide does.......appears to me that he used low firing glaze as is done in raku and fired it around 1080-1100C (Cone 03) to get that much movement in the glaze In other photos of his work you can see the remains of twisted wire spirals on the shoulder of the pot where the wire has partially melted green and partially burnt black where it protruded from the glaze layer.......very exciting work! Irene Link to comment Share on other sites More sharing options...
AWPottery Posted February 9, 2014 Author Report Share Posted February 9, 2014 Thank to everyone that replied. This seems like something fun to experiment with the next time I raku. I think I'll try it. Link to comment Share on other sites More sharing options...
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