David Donica on tue 21 jan 97
Would like any info/input anyone has about glazes containing cobalt carb.
being food safe? I'm new to this list and really appreciate all the info-
I had the pleasure of briefly meeting Mr. Roy at NCECA in Diego 5 years
ago- you're still a wealth of knowledge!!!
Mt. Shasta, Calif.
Ron Roy on wed 22 jan 97
My books indicate cobalt is not much of a danger but you don't want to be
sprinkling it on your cereal. Send me your glaze recipe and the cone you
fire to and I will give you my opinion about the integrity of your glaze.
Evenings, call 416 439 2621
Fax, 416 438 7849
David Donica on thu 23 jan 97
The cobalt-containing glaze I had questions about is called Gloss Blue, I
got it about 15 years ago from the studio where I first was introduced to
clay. I volunteered to mix glazes and in looking up the recipie, this is
what I had (^10R):
Feldspar: 2175 43.5
China Clay: 100 2
Silica: 1362.5 27.25
Whiting 137.5 2.75
Colemanite: 450 9
Dolo: 450 9
Zinc: 100 2
Barium: 225 4.5
Tin: 125 2.5%
Cobalt: 50 1%
If you add up all but the last two ingredients, you get 5,000 gms so I
divided everything by 50 to bring it to 100 which yields the second column.
I then took what percentage of 5000 was the tin and cobalt for those two
percentages in the second column. Is this correct?
Then there's the oops when I noticed the glaze contained Barium, which I
know is a no no for food items- is Barium contraindicated in any amount?
And alas, the question of what can I substitute how much with apologies if
this is redundant. Lastly, what would be a good text for a glaze neophyte
such as myself- I am intrigued by Robin Hoppers book, The Ceramic Spectrum
which I haven't really reviewed- any comments? Many thanks.
Mt. Shasta, Calif.
Patsy Catsos on fri 24 jan 97
I was reading a dog food label at the supermarket yesterday and I was
surprised to see that cobalt carbonate was listed among the ingredients! I
would guess that its not toxic in tiny amounts.