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our community college cone 6 glazes

updated mon 30 apr 01


Helen Bates on sun 29 apr 01

Dear Clayarters,

I have a favour to ask you all to think about, if you feel you have
anything to contribute, but especially those who are familiar with
Tucker's Cone 6 clays, particularly the Mid Cal 5, the Mid Smooth
Stone, the MCS porcelain, all of which are used in my local community
college where I take an extension pottery course or two most terms.

Like a lot of potters, as I have been reading, our glazes have some,
to a -lot- of Gerstley Borate. Naturally, we aren't going to be able
to order more, or even if we did order some from C. Gatto, even her
supply will come to an end.

I know very little in a practical way about glazes. All I've done is
help mix one or two at a course in another centre. We "continuing ed"
students have not, historically, been involved in making or even
mixing glazes.

There is no full time pottery and ceramics course here. What this
means is that there is no full time staff, either pottery teachers or

Teachers are hired on a contract basis for 2 or 3 courses a term, and
may be in the facility teaching perhaps 6 - 10 hours a week. They
also have private studios, from which they gain much of their income,
or also teach in another city.
Our technician works usually two 8 hour days per week making up
glazes, pugging reclaimed clay, firing the kilns and other such jobs.
Part of her "pay" includes being able to make ware in the studio if
the above work is under control. She also has a non-instructional
open studio once a week for 3 - 5 hours during her regular work day.
Although it's "non-instructional", she gives people quite a lot of
help if they ask or if they appear to be in difficulties.

So, no-one has much time available for extensive glaze testing. We've
made a start (not me, though I "kibbitz") with a non-gerstley glaze
that was nice in one version. A triaxial (?) O O O O O O line blen=
seemed to give a few
results, but a vinegar test o o o o o showed leaching in the
nice satin
blue (kind of denim blue), as well o o o o as crazing. As well, the
opaque white we made seems rather o o o "dry." Back to the
o o

I am trying to help find out if there are ways to speed the process.
I have downloaded some information already, and I will pass it on to
my teachers (I have something on the theory of cone 6 glazes, clear
and matte, from Digital Fire, and some from several potters' and other
sites on the www.

What I think would be really helpful is that if people out there are
able and willing to suggest a really promising base glaze that can
then be tested with additions of oxides by us, especially one that
will be able to hold up to the various demands made of a "school"

For instance, our glazes have to be temperature flexible, though
nominally we fire at cone 6 (Orton, I believe.) It would need to be
stable in thick applications, because many of our students are
beginners, or near-beginners. It would need to allow for
"double-dipping", and it would need to be not too sensitive to the
presence of wax emulsion on the foot.

I have copied our current glaze recipes onto our hard drive, and can
upload them in a subsequent post, or send them privately to anyone
willing to look at them. I believe they may date from the 1970's in
some cases, or the 1980's, perhaps.

Our technician was trained in her job by previous pottery course
teaching incumbents and the glazes she mixes up are ones she was
taught by them, and has learned to deal with over her own time at the
college. She is not trained in glaze analysis, and only recently has
had some opportunity to observe a weekend course in colour line

Our teachers no doubt are qualified in some degree or other to develop
new glazes(I think one is, especially), but as I have said, they are
not employed for many hours a week, and they use different clays and
glazes in their own work.

Well, any suggestions or help would be wonderful. I apologize for
asking for "cribs" so to speak, but I think the process of going at it
completely from scratch, is going to be a daunting process.

(I don't think suggesting Digitalfire or other glaze programs will
help me, because my basic glaze-making experience is so limited, and I
can't suggest it for my teachers because one hasn't a computer and the
other isn't using hers for much more that doing email.)

(If some of the Ontario potters on the list who use Tucker's clay are
willing to help out, I'll be especially grateful.)

Thanks in advance,


Helen Bates

Helen Bates