[Clayart] Cobalt toxicity

ronroy at ca.inter.net ronroy at ca.inter.net
Wed Sep 1 23:13:55 UTC 2021

Thanks Eric,

You may wish to do a small 5 part line line blend to see if reducing  
the cobalt will still still give you the result you want. The savings  
may be worth the trouble.


Quoting Cynosure -Arts <cynosure_arts at hotmail.com>:

> Thank you to all who weighed in on my earlier post (especially Ron Roy).
> After much additional googling, this is the best I could find for  
> recommended maximum exposure to cobalt taken orally:
> Although the US Food and Drug Administration (FDA) has not developed  
> an acceptable daily intake for cobalt, the United Kingdom Expert  
> Group on Vitamins and Minerals concluded that supplementation with  
> 1400 ?g Co/d was unlikely to cause adverse health effects in adults  
> (8). The European Food Safety Authority has suggested a safe intake  
> of 600 ?g Co/d for noncarcinogenic effects.
> (American Journal of Clinical Nutrition)
> Further, the EPA has NO guidelines for cobalt concentration in  
> drinking water. for comparison.
> The test I had run on the Rhodes Black glaze fired to Cone 10Redux  
> (see glazy.com) at BSC Labs showed a result of .278 mg/L (or 278 ug).
> This seems to fall well within 'safe' guidelines.....am I reading that right?
> Of course, all the other variables of application and firing may  
> make these results inapplicable for other users, but it does imply  
> the glaze is generally acceptable as a food surface.  And I'll also  
> add that the home alkali test (simmered in a soda ash solution)  
> produced no surface change, so okay for the dishwasher.
> Eric Newman
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Ron Roy
ronroy at ca.inter.net
Web page ronroy.net

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