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^6 Copper Red Glaze Oxidation


Kathy321

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I just came across and article on cone 6 copper red oxidation glazes by Robert S. & Beatrice Pearson:

http://tinyurl.com/n4hubb6(and attached)

Before I start experimenting...

Has anyone tried any of these recipes and know how they behave?

The recipes use General Colour Frits 114, 146, 154 & 156. Does anyone know if there are Ferro frits that would substitute?

I would also like to know whether they are food safe.

Thanks!

Kathy

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  • 3 years later...

So it looks like the General Color company sold off their ceramics division in 2003.  The company who bought that division was not interested in pottery and mainly does enamel coatings / window treatments etc.

It looks like there is a Ferro frit that is an approximation for one of the mixes, the other ones are maybe more problematic but maybe another frit wouldn't be so bad.  The main thing I am wondering about is the Silicon Carbide.  Does anyone know the approximate particle size distribution of the original?  It is widely manufactured but with the wrong size it might burn off too fast (if too small) or not be effective at reducing the copper (if too big).

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There were some interesting discussions and starting points regarding silicon carbide in this thread. One poster had some very good results using 1200 mesh, but he mentions that he wasn't able to continue his investigations. Some posters mentioned that you need to use a light hand with the material, as it can cause severe blistering and boiling. Joseph, who was using 1200 mesh, reported far less bubbling, and only some small pinholing.

 

 

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I will just say be prepared for a lot of work and testing. When I was doing currie grids of local reduction using silicon carbide, I noticed that small % changes in silica and fluxes made drastic differences in the amount of reduction you get, so there is a lot more to it than just adding some silicon carbide and calling it a day. This means that some glazes might have 0 reductions visible but if you added or subtracted small amounts of flux or silica it might instantly start reducing. I had some tiles on my grid be completely red while the tile above/below it had no evidence of reduction happening.

Then on top of that, you always have this issue of thinking about pinholes and bubbling. Not to say it isn't possible to get perfect results, I am sure it could be done, anything is possible, it just depends on how much effort you want to put into it. Another thing I noticed is how thick the glaze is, the thicker amounts of glaze I had more reduction than when the glaze was thin. I don't know all the science behind what goes into it all because after testing for about 10 or so firings I was completely baffled. 

I don't want to be negative, just giving you some realistic ideas to explore.

Get a fine mesh silicon carbide, much less bubbling than the lower meshes I tried 600 and it was just disaster lava glaze compared to 1200.

Take really good notes and last of all! Share what happens! Not enough people come back here and share how their testing goes!

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I also ran tests way back in 80's or early 90's, seemed that things were very finicky, and you had to keep everything stirred up well or you got puke greens or worse. Lots of times the color would be good, but the pin-holing would by unacceptable. Some day maybe someone will come up with a local redux frit that will help with the problems.^_^

 

best,

Pres

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18 hours ago, Magnolia Mud Research said:


Neil, et .al., 
remember that silicon carbide is a material used as a strong high temperature refractory, aka kiln shelf.   The oxidation of a  silicon carbide particle produces a coating of silica, aka silicon dioxide, which functions as a barrier for the oxidizing agent.  

LT
 

Perhaps my terminology was poor, but I think you understand what I'm getting at- allow the reaction to happen before the glaze goes into melt. In reading the Turner article last night, he actually does a hold at 1800F for 30 minutes for that very reason.

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