Hello -- I'm fairly new to the group and I am enjoying it inmensly. I know Copper Oxides added to a base and fired in reduction will often result in reds. I was wondering whether or not just applying the oxides as powders will produce the same effect?
I assume you mean adding water to the copper oxide and painting it on - and yes it will but beware that what you are going to get is anything from green to red and some possibly UGLY inbetween colors. Since copper is green in oxidation and red in reduction the color is very much dependent on the dance, prayers and sacrifices you offer up to your kiln G~d before hand (and what mood the weather G~d is in) :)
Also it is worth noting that copper reds work best when the oxide/carbonate is actually quite a small percentage in the glaze. Painting raw oxide on will only give you an almost black metallic surface.
what are the mechanics of copper that make it unsafe? i've been hearing that recently but don't know why. the old fashion copper molds for various food date back a number of centuries.
I went to find my cone 6 glaze book and I have lost it :( However I did a search and found this, it was a clayart thread but I am sure posting the link is acceptable
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comments underneith the chart are particularly helpful and IMO safe practice. Cheers
[Copper's toxicity isn't as bad as some metals (like lead) but it's not good for you. Here's a MSDS:
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. The molds and pans you're remembering were generally tinned on the inside. Tin isn't very reactive, and it goes onto hot copper like melted butter, leaving a thin protective layer behind.And just becasue something was done, it doesn't mean it was a good idea; Beethoven, for instance, was found to have had elevated levels of lead in his blood, likely from drinking (slightly acidic) beer from lead-pewter steins, which were common in his day. This is blamed for many of his chronic health problems:
Actually the MSDS you linked to refers to copper metal, a slightly more relevant one addressing Copper Oxide can be found at this link:
which gives a little more detail regarding hazard warnings, risk phrases, etc. American data sheets more or less agree with the above but are less clear e.g.:
daily copper requirement has been estimated at 30 micrograms/kg ofbody weight for an adult. After ingestion, maximum absorption of copperoccurs in the stomach and jejunum.Copper is bound initially in the serum to albumin and transcuprein,then later is bound more firmly to ceruloplasmin, which binds more than75% of circulating copper.Absorption is increased in copper deficiency and is impaired insmall-bowel disease.Copper is distributed throughout the body but is stored primarily inliver, muscle, and bone.The normal concentration of copper in blood plasma is 1 mg/liter.In all mammals, copper is an essential trace element involved in :-fundamental cellular respiration,-free radical defense,-connective tissue synthesis,-iron metabolism,
The key difference between things like iron and copper on one hand, and lead and barium on the other, (and why I make the comparision), is that there are no minimum dietary requirements for lead and barium. That sets these materials in different categories.
Our copper plumbing does not replace the dietary copper missing from our modern petrochemically produced foods. You need something acidic to make it soluable. If you are greatly afraid of your copper glazes, that are otherwise well formulated, don't drink orange juice from it. Keep it for milk.. ;^)
Always wear a mask when dry mixing glazes. DO NOT BREATH ANY DUST! Our number one health hazard as far as our materials go is silicosis.
You are absolutely right. Though I wonder if there have been studies done about ingesting a little too much copper over prolonged periods. Something I would not want to test out :o) I do have concerns about unsafe glazes I guess and of course copper and iron are safe compared to barium and lead, but I think it is a good idea to have good practice for all our glazes. I have often seen bowls for sale with matt barium glazes, ya know what do you do?
As I mentioned, there has been studies showing that our dietary copper is being leached out of our food, because of the use of petrochemicals as fertilizers and pesticides. Our daily intake of dietary copper is not sufficient.
Depleted copper in the soil and foods may help cause diseases like BSE and other nevrvous system diseases:
Consequences of manganese replacement of copper for prion protein function and protease resistance:
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related: Anticeptic qualities of copper surfaces in:
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