Gregory D Lamont on tue 29 jun 99
I'm resubmitting this to the group because the lack of response to my
initial inquiry made me suspect that it might have been missed. I have
always mixed my own glazes with varying degrees of success. I was never
much interested in using commercial glazes as they always looked quite
uninteresting--no variegation, mottling, etc.--especially in electric
firing. Recent print ads for a series of Opulence Cone 6 glazes
manufactured by Mid-South Ceramics that claim "reduction look in electric
fiiring" have prompted me to see what they're about for myself. The glazes
were quite creamy and applied very nicely. The fired results--despite a
slight overfiring (cone 7 well bent in the sitter) were quite nice. While
they might not be mistaken for true reduction fired glazes, they had the
nice surface interest that most other commercial glazes seem to lack.
So, again, my questions are these:
How does a commercial glaze differ from a typical "homemade" glaze?
How do the manufacturers of commercial glazes make their glazes such that
they apply well enough and give fired results satisfactory enough that the
manufacturers aren't inundated with dissatisfied customers demanding
refunds for glazes that are crawling, cracking, etc.?
Are there special processes, chemicals, or additives, that they put in
their glazes to ensure performance?
Can anyone give me a recipe for a typical cone 6 without, of course,
divulging the name of the glaze or the manufacturer?
TIA,
Greg Lamont
gdlamont@iastate.edu
http://www.ourwebpage.net/greglamont/
3011 Northwood Drive
Ames, IA 50010-4750
(515) 233-3442
Mike Bailey on fri 2 jul 99
In message , Gregory D Lamont writes
Dear Greg,
>----------------------------Original message----------------------------
>I'm resubmitting this to the group because the lack of response to my
>initial inquiry made me suspect that it might have been missed.
Sorry Greg, I thought some of the regulars would pick this one up.
Anyway, you can have a few comments from me as I make the glazes for our
pottery supply business.
Snip
>
>So, again, my questions are these:
>How does a commercial glaze differ from a typical "homemade" glaze?
snip.
In many cases they don't differ. It's just that the manufacturer has
taken some care to use finely blended materials, using a combination of
materials that gives a chemically well-balanced glaze. Attention is also
paid to ingredients that have practical benefits for the glaze in its
slop form re suspension etc.
Making these well-balanced glazes is the easy bit - but many potters
want to use anything but shiny, transparent glazes. This then might take
one into alumina matts which, by just increasing the clay content again
doesn't give too many problems in use. The main problem area is the
crystal forming, low clay glazes which are far more temperature
sensitive and, of course, tend to run. Teaching ones customers how to
use them needs a combination of patience and tact!
In the industrial world the large manufacturers also supply earthenware
glazes that have been fritted and milled in slop form.
>How do the manufacturers of commercial glazes make their glazes such that
>they apply well enough and give fired results satisfactory enough that the
>manufacturers aren't inundated with dissatisfied customers demanding
>refunds for glazes that are crawling, cracking, etc.?
You obviously look at the world with a positive attitude. The reality is
that while not plagued with complaints, manufacturers receive a steady
stream of problems - some of their own making and some arising from the
customer getting it wrong (but not knowing why!)
An explanation that has to be given in many different forms concerns the
fact that we supply many clays and glazes. They may or may not be
compatible with each other or with the customers firing regime.
Disabusing customers of the notion that "because we supply it, it must
work" is a daily task! I try and develop the concept that finding all
this out is part of learning the craft - finding out what works for you.
>Are there special processes, chemicals, or additives, that they put in
>their glazes to ensure performance?
I'm not sure that this is a regular feature. I've heard of some
manufacturers adding some glaze binder.
>Can anyone give me a recipe for a typical cone 6 without, of course,
>divulging the name of the glaze or the manufacturer?
Here's a well behaved ^6 glaze
Any feldspar 46
China clay 5
Bentonite 2
Whiting 17
Zinc Ox 5
Silica 25
We don't actually make this one. Everyone in the U.K. uses ^8 so our
glazes are for a notional 1260 deg C.
Cheers,
Mike
--
Mike Bailey. Bath. U.K.
Martin Howard on sun 4 jul 99
We don't actually make this one. Everyone in the U.K. uses ^8 so our
glazes are for a notional 1260 deg C.
No Mike. Some use 02-1 and there are clays and glazes for that range,
supplied by large firms, here and in Germany. Please do not persuade
more potters to use high cones, leaving us on the lower, more
economical, more green levels, still more lonely. Cone 01-1 might be the
growing point of ceramic pottery in the UK. Well, one can always hope.
Martin Howard
Webbs Cottage Pottery and Press
Woolpits Road, Great Saling
BRAINTREE
Essex CM7 5DZ
01371 850 423
araneajo@gn.apc.org
Mike Bailey on wed 7 jul 99
In message , Martin Howard writes
Dear Martin,
Of course, you are correct. I suppose I was exaggerating to make the
point that most potters in the U.K., who do stoneware, use^8.This is in
contrast to our cousins in the USA et al who do a lot at ^6.
The work I'm doing with my glaze testing buddy David Hewitt at ^6
suggests that there's a lot we can do in the UK to drop our firing
temperature by a couple of cones.
Cheers,
Mike Bailey.
>----------------------------Original message----------------------------
>We don't actually make this one. Everyone in the U.K. uses ^8 so our
>glazes are for a notional 1260 deg C.
>
>No Mike. Some use 02-1 and there are clays and glazes for that range,
>supplied by large firms, here and in Germany. Please do not persuade
>more potters to use high cones, leaving us on the lower, more
>economical, more green levels, still more lonely. Cone 01-1 might be the
>growing point of ceramic pottery in the UK. Well, one can always hope.
>
>Martin Howard
>Webbs Cottage Pottery and Press
>Woolpits Road, Great Saling
>BRAINTREE
>Essex CM7 5DZ
>01371 850 423
>araneajo@gn.apc.org
>
--
Mike Bailey
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