[Clayart] Cobalt toxicity

Edouard Bastarache edouardb at colba.net
Thu Sep 2 16:35:44 UTC 2021

*Sorry I forgot to give the URL,
It is in my next message

-----Message d'origine-----
De : Clayart [mailto:clayart-bounces at lists.clayartworld.com] De la part de
Edouard Bastarache
Envoyé : 1 septembre 2021 22:56
À : 'Clayart international pottery discussion forum'
Objet : Re: [Clayart] Cobalt toxicity

Cobalt technology and toxicology

Edourd Bastarache

-----Message d'origine-----
De : Clayart [mailto:clayart-bounces at lists.clayartworld.com] De la part de
ronroy at ca.inter.net Envoyé : 1 septembre 2021 19:14 À : Clayart
international pottery discussion forum Objet : Re: [Clayart] Cobalt toxicity

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
> 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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