clay lover Posted March 19, 2015 Report Share Posted March 19, 2015 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? Link to comment Share on other sites More sharing options...
Mark C. Posted March 19, 2015 Report Share Posted March 19, 2015 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 Link to comment Share on other sites More sharing options...
Marcia Selsor Posted March 19, 2015 Report Share Posted March 19, 2015 I have gotten a wide variety of copper carb. it is my main colorant in saggars so it gets used. I had some from one supplier that was a little courser than other suppliers cu carb. I am not too picky about it because it is not in a glaze. Marcia Link to comment Share on other sites More sharing options...
Cavy Fire Studios Posted March 19, 2015 Report Share Posted March 19, 2015 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. Link to comment Share on other sites More sharing options...
Babs Posted March 19, 2015 Report Share Posted March 19, 2015 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... Link to comment Share on other sites More sharing options...
Mark C. Posted March 19, 2015 Report Share Posted March 19, 2015 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. 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 Link to comment Share on other sites More sharing options...
jrgpots Posted March 19, 2015 Report Share Posted March 19, 2015 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 Link to comment Share on other sites More sharing options...
PeterH Posted March 19, 2015 Report Share Posted March 19, 2015 Good post. For the record can you edit the typo in the formula for Malachite, Cu2Co3(OH)2 => Cu2CuO3(OH)2 Link to comment Share on other sites More sharing options...
clay lover Posted March 19, 2015 Author Report Share Posted March 19, 2015 so the lighter color green has the MOST copper? That knowledge will help direct testing, perhaps. Test in 1% increases-decreases? Link to comment Share on other sites More sharing options...
PeterH Posted March 19, 2015 Report Share Posted March 19, 2015 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 Link to comment Share on other sites More sharing options...
TJR Posted March 19, 2015 Report Share Posted March 19, 2015 Copper carb used to be a DARK green. It was a bit unsettling to use mint green. Didn't affect the colour of the on glaze brush decoration. But you gotta test it. Tom. Link to comment Share on other sites More sharing options...
oldlady Posted March 19, 2015 Report Share Posted March 19, 2015 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.) Link to comment Share on other sites More sharing options...
clay lover Posted March 20, 2015 Author Report Share Posted March 20, 2015 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. Link to comment Share on other sites More sharing options...
drmyrtle Posted March 25, 2015 Report Share Posted March 25, 2015 I went out to the garage and found this ore sample. Wow! Is that what I might find in my garage if I clean it out? Link to comment Share on other sites More sharing options...
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