Cobalt Carbonate

[kenthenricksen]

Hi Everyone!

 

 Is Cobalt Carbonate food safe?  I have been using as a wash on top of a white glaze with good results.  My only question is if it's food safe. I've been firing to cone 6.

 

Thank you!

 

 

 

[Marcia Selsor]

if it has melted into the glaze, there should be no problem. It should work as an underglaze and that would most definitely be food safe. If you get a thick stroke of cobalt carb. that has turned crusty on the surface , then I may be concerned..

Marcia

[Pres]

Cobalt Carbonate is poisonous, and therefore needs to be used with caution. This includes the handling, and storage. When dealing with a wash over a glaze, and using Cobalt of any sort you first must make certain that your glaze that you are washing with the cobalt is food safe, that is the glaze does not degrade, under acids, or bases. If it does, then the Cobalt wash will also be of concern. All items labeled as food safe should have testing preferably a commercial lab. If uncertain check your glaze with using a lemon slice(acid) in a bowl, and a concentrated solution of dishwasher detergent(base-alkali) and water in another bowl or plate. These two tests will show after a few days if there is they have any effect on the glaze. If the glaze does anything-changes color, crackles, fades, becomes less glossy, yellows, or anything, then the two components or at least one of them is effecting the glaze and the glaze is not food safe. Further testing is needed to be certain. 

 

I test my test tiles with vinegar, and the dishwasher solution in glass dishes. By immersing part of the tile for several days, I can see if there is a line between the area dipped and the undipped. makes it easy to see a change.

 

 

best of luck,

welcome to the forums

 

best,

Pres

[Mark C.]

I would suggest not eating it-under glazes its fine even in most glazes-if your wash melted into your glaze you are ok as well.

Testing is best as Pres says