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New Copper Carb A Way Different Color!


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I ordered a lb. of copper carb and it doesn't look anything like the bag I have been using for 2 years.  Old bag is mint green, pale. pastel.  New bag is bright strong bluish green, almost like Spring grass.  I called the supplier, asking how to use it, and was told, it's not different, it should require no adjustment to amounts used.  What do you guys think?  I know, it's test, test, test, but where to start?

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Do not sweat it. Over the years many colorants colors have shifted due to mine and country  of origin etc. These are mined materials which are always changing.

For example for many years colbalt carbonate always was one color and when many suppliers shiifted to Chinese colbalt carb the color was way different but the results where the same. Test if you like (always a good idea) but I would not sweat it on color alone.

Mark

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I'd test it, just in case. Seattle Pottery sent me a bag of "EPK" and it was a completely different material--TALC. They swore up and down it was just off-color EPK, but I had the good sense to test it. Omg, it turned my shiny clear into a matte, moon-cratered NIGHTMARE. Their "100% reassurance" could have cost me my whole kiln load if I didn't test it! Hard lessons, buddy. :D

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Yes I have had differetn looking copper carb over the years. And I have had different colour outcomes in glazes moving a bright turquoise glaze towards a much greener glaze...

Wish there was an answer other than test and Mark's soln. buy heaps at the beginning...

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I'd test it, just in case. Seattle Pottery sent me a bag of "EPK" and it was a completely different material--TALC. They swore up and down it was just off-color EPK, but I had the good sense to test it. Omg, it turned my shiny clear into a matte, moon-cratered NIGHTMARE. Their "100% reassurance" could have cost me my whole kiln load if I didn't test it! Hard lessons, buddy. :D

This is often the case as bags get shipped marked on invoice as A but the shipping guy sends a bag of B.

Things like EPK I buy in full 50# bags so you know the bag is right-materials in smaller broke down bags can get mixed up so checking them out is always a good idea.

Its really hard to get good these days day as well so wrong info is way more common now .We have all seen this shift-now I'm talking like one who has been around for decades.

Mark

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Trying to remember my geology, Malachite, Cu2Co3(OH)2, is a mint green and azurite,Cu3(CO3)2(OH)2 is bright blue. Both are forms of copper carbonate. The differences in color comes from the differences in % of each of these two. Of the two, azurite has more Cu per molecular weight. That would mean that the mint green color has more Cu by weight. It would make sense that glaze colors would change as well.

 

I went out to the garage and found this ore sample. The light green is malachite while the deeper blue is azurite. Both exist in the same ore sample.

 

Like always, test, test, test.

 

Jed

post-26461-0-16374600-1426740526_thumb.jpg

post-26461-0-16374600-1426740526_thumb.jpg

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so the lighter color green has the MOST copper?

 

 

Looking on wikipedia I get:

 

Azurite has 3 copper atoms in a formula weight of 344.67. 344.67/3 = 114.89

 

Malachite has 2 copper atoms in a formula weight of 221.1. 221.1/2 = 101.55

 

So (114.89/101.55) = 1.13 grams Azurite would replace 1 gram of Malachite

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this change shook me up, too.  i had the original 5 pounds of a greyish green material that seemed like ground rock.  the latest stuff is a bright color that seems like a powder of some kind, maybe lime Kool-aid.  it does not seem as strong as the original.

 

(no, i am not going to drink it.) ;)

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Old lady, that comment gives away our age, ya know. 

 

Good to know you did not see much if any, change in finished work, but I will mix small and test , for sure!

I am glad to hear that others have been set aback by getting different, darker green copper. 

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