Helaine Melvin on wed 21 apr 04
My fellow clayarters. I have been lurking in the shadows for many =
moons, make that years, and, at the risk of being annihilated for =
opening my mouth I wanted to offer up my thoughts. I work primarily in =
the ^06 range but have been venturing into ^5 and even attempting my =
own glazes. I have been aware of the lead release problem with the =
supposedly food safe glazes since California changed its lead laws in =
the early or mid 80's. I worried a great deal then that I might =
inadvertently become a typhoid Mary by selling work that was not safe =
for my customers. In those early days most of them were family and =
friends and my mother would have given me hell if I had inadvertently =
done in Uncle Phil, of course maybe Aunt Alyce would have thanked me. =
So I began researching what to do. I had just attended an NCECA =
conference in San Jose and met some really wonderful and informative =
people. I had many telephone conversations with people in the Western =
states and I remember Mile Hi Ceramics in Colorado was particularly =
helpful. This is pretty long winded but to get to the point, I =
discovered that when using lead in glazes - and mind you, this was =
fritted lead -supposedly "safe" stuff - that it gets absorbed into the =
fire brick of the kiln. Then it gets onto pieces which are =
subsequently fired in that kiln. I bought lead sticks by the bags full =
and tested pieces and brick and that little pink color kept coming up. =
I sent my work to a lab up in central California and it came back with =
traces of lead even though I had changed the glaze to a lead free =
formula. I remember arguing with the company but they said it is what =
it is. The guy who I used as an advisor suggested making crucibles of =
high fire clay and putting copper carbonate in them and firing the kiln =
I think to ^6. I did this twice and it did work in attracting the lead =
in the brick and pulling it out. I don't know the chemistry but my lead =
sticks came up clean. The Copper Carb also ate through the crucibles and =
ruined my shelves. I have purchased new kilns since then and NEVER =
use any lead in my studio. I also sold those old kilns to someone who =
was slumping glass for lamps so I feel that I was not just passing the =
problem to someone else. (Don't I sound noble!) I'm not.
I know that I, as most of you, have eaten on lead glazed plates and =
bowls growing up. My mother, bless her soul, would never throw away a =
tea cup - depression era mentality I guess- and I drank tea out of many =
glued together cups - which I would never do now. Times were different =
and we are now bombarded by many more things in our modern world. I =
still can't get over that we've turned our cattle into cannibals. Jeez. =
Ethics have gone to hell and profit is the new golden calf. - a little =
I just wanted to pass on a little of what I've learned. I think that =
the kilns become compromised when toxic materials are used. I am =
expecting a full blown chemistry lesson from some of you smarty pants =
out there but I think I can take it. =20
Just one more thing while I am bravely speaking up. Out here we only =
have ^5 clay from Laguna which is our primary supplier since they have =
gobbled up several of the old "indie" ceramics suppliers. It's strange =
that they supply the rest of the country with ^6 but not us in their =
home state. Aardvark, I know you're out there but a very long trip for =
me. All you guys keep using the ^6 recipes. I have John & Roy's glaze =
book and took Ian Currie's glaze workshop but I'm unclear as to how to =
exactly alter the recipes. I know, there's no magic, it's just keep =
reading and testing.
Lastly, I want to speak out for those of us who are low fire ceramists. =
I love that I can use the pieces as a vehicle for painting and drawing. =
It is a different animal than the beautiful flowing chemistry of the =
higher fire work but please we are family. We also love to work in that =
fickle medium and I feel that many of you dismiss us. I love it all. =
Can't we all just get along?
Thank you for your insights. I'll go back to my corner now.
In the heart of L.A. just South of Hollywood.
John Hesselberth on thu 22 apr 04
On Thursday, April 22, 2004, at 12:35 AM, Helaine Melvin wrote:
> I have John & Roy's glaze book and took Ian Currie's glaze workshop
> but I'm unclear as to how to exactly alter the recipes. I know,
> there's no magic, it's just keep reading and testing.
Thanks for joining in--I hope we hear more from you in the future. To
try to answer your question, some of our glazes will be fine at cone 5.
Others probably need a full cone 6. For those, adding a little more
boron or zinc (depending on what is in them already) should do the
trick. If you have a specific glaze or two you would like to try send
Ron or me a note off-list and we'll suggest a modification.
Snail Scott on fri 23 apr 04
At 09:35 PM 4/21/04 -0700, you wrote:
>...Out here we only have ^5 clay from Laguna which is our primary supplier
since they have gobbled up several of the old "indie" ceramics suppliers.
It's strange that they supply the rest of the country with ^6 but not us in
their home state.
Actually, a lot of Laguna's clays are great at ^6.
When they put out their catalog, they put the clays
into categories of ^06, ^5, and ^10, and publish the
stats for the clays at those temperatures, but that
does not mean that those are the optimum vitrification
temperatures for those clays. It only means that they
tested them at that temperature. Give them a call -
they can be very helpful.