Ooops, Cobalt Carbonate instead of Cobalt Oxide

[Chantay Poulsen]

I had posted a recipe and test results last month for a glaze called Dave's Blue.  Today I went to mix up another batch.  I realized that I used Cobalt Carbonate instead of the listed Cobalt Oxide.  The glaze looked good and fired well.  I don't know enough about chemistry, but can anyone see a problem with this sub?  I don't even have Cobalt Oxide, $$, and plan to continue to use the recipe with the cobalt carbonate.

[Jeff Poulter]

Cobalt oxide is about twice as strong as carb & tends to speckle more whereas the carb seems more uniform in color.  It depends on the recipe.  There are some that I only use oxide and others where I use carb.  If I have to sub, I usually use 1 1/2 to 2 times as much carb as oxide depending on the recipe.  The good thing is that a little cobalt, no matter what the form, goes a long ways!  jhp

[Nadine Mercader]

Jeff hit it dead on.  I would like to see samples of the previous glaze and this new one.

[Chantay Poulsen]

I'm only making the glaze with the cobalt carbonate.  I don't have any cobalt oxide and it will be a month or so before I can get some. $$.  I will post test tiles after I fire this batch.  There is a pic on Insight live with the recipe. OK, found pic of previous test batch that used the cobalt carbonate.