Bob Masta on wed 18 aug 04
First of all, many thanks to WayneInKeyWest for
recommending Ceramic Industry magazine.
This free trade publication is usually, as the name
suggests, oriented more toward industry ceramics than
toward pottery as practiced here on Clayart. But it's
fun to see what the big boys are up to, and every now and
then a few gems turn up. The August 2004 issue includes
(at least) two articles that I think Clayarters may be
interested in.
First, on page 9, is the brief article "Plaintiff and
Defendants Agree to Tenative Settlement in Proposition 65
Drinkware Cases" by Andrew Bopp. The case is about lead
exposure from drinkware, and the settlement apparently
covers issues like consumer warnings as well as weight of
lead in decorating materials. The line that caught my
eye was "There are also restrictions with respect to the
use of lead and cadmium in the lip and rim area of
drinkware (rim and top 20 mm of a drinking vessel).
There are also separate requirements for ceramic mugs,
which are to be tested according to a specified
protocol." Just a heads-up for those who still use
lead-based glazes, even if only as exterior decoration.
The article I found most interesting was "Got Crazing?
Try Sealing Your Feet" by Christine L. Grahl, who is the
editor of Ceramic Industry. It's about a company called
Elias Ceramics and their product
called Cerama-Seal. You apply this to the foot of
greenware, and it vitrifies with the body in the bisque
firing. Then you can use low-fire glazes and still avoid
crazing in functional ware. Surprisingly, you don't need
stilts: the stuff apparently won't cause the foot to
stick to shelves, in either the bisque or glaze firings.
They claim that test pieces have been through boiling and
multiple freeze-thaw cycles, and they say that "the
results have indicated that the coated ware is durable
enough for use in year-round outdoor applications, even
in regions with cold winters." The article also suggests
that this coating could be applied to the inside of raku
vases to make them functional.
This seems to fly in the face of the oft-heard advice
that no amount of careful glaze application will protect
a porous body from eventually crazing. I don't know what
the situation is here. Perhaps in time these products
will still craze. Maybe it's a difference in standards
for the life of a piece, based on the intended use.
(They make a lot of pet bowls, for example.) But it
is certainly something to think about, especially for
those wishing to move to low-fire, either for reduced
energy costs or for access to different glazes.
I've done a few experiments with forced low-fire
vitrification myself, which are definitely at a
"preliminary" stage. I'm more interested in vitrifying
the whole piece clear through, but this development is
certainly encouraging. I for one would sure like to know
what's in the magic stuff. Any educated guesses?
PS: I have no connection to the magazine or company!
Bob Masta
potsATdaqartaDOTcom
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