mel jacobson on tue 23 may 00
here is the text.
it is easier than 40 emails.
mel....
SIDEBAR
Reg Behrends
I have been a production potter for more than twenty five years. My wife
Mary and I run the Blue Moon Pottery in Drummond, Wisconsin and sell to
galleries and shops across America. I produce mainly glaze ware and need a
dependable, attractive glaze.
In the early eighties I was attending a workshop at the University of
Wisconsin "Pigeon Lake Art Camp", and was discussing cone 6 glazes with
Mel Jacobson, it was suggested that I try using volcanic ash glazes in my
commercial pottery. Mel said that it was simple, easy to measure and had
a very high rate of success. I am happy to conclude after using it for
fifteen years that I have less than 1% loss. We are using the ash glaze
almost exclusively with a mixture of 65% volcanic ash and 35%
gertsley borate.This glaze (I call it Mel's), is transparent, fluid, but
does not run off the pot, accepts most colorants, and works like magic in
combinations over matte glazes.
I use plant impressions on some of my pots, Mel's glaze lets the finest
details show through and breaks thin on the edges to highlight the
design. This glaze has the richness at cone 6 in an electric kiln that I
have not had since I was firing cone 10 reduction with wood.
VOLCANIC ASH GLAZE by MEL JACOBSON
In seeking a simple yet beautiful glaze that I could use in a full time
high school clay program I stumbled over a small article by Richard Behrens
about the use of pumice as a glaze material. This was in the early
seventies and colmanite had changed and gertsley borate was becoming
the mid-range flux of choice of many potters. Behrens suggested using
combinations of volcanic ash with gertsley borate to create a variety of
temperatures for a simple, yet effective glaze. This began a long study to
find a solution to our glaze needs. Then with the explosion of Mount Saint
Helen's, and the publicity related to the abundance of volcanic ash we
decided that we had our glaze. High school students loved the idea of using
a material that nature blew out of a massive rupture in the earth. It
helped them understand how the whole process of nature melting earth was
what they could do in a studio with a kiln and their pots.
We began with a formula of 60% volcanic ash and 40% gertsley borate. In
the early stages we fired to cone 4 and used the clear glaze to cover
other commercial glazes and stains. Soon however we were adding iron,
copper, and cobalt and with the addition of zircopax we began to achieve
opacity.
As a result of a mistaken cone placement we found that we could fire to
cone 6 without running the glaze. Our next experiments found us firing the
glaze to cone 1. It was slightly matte, but still very usable. At cone 6
it has a natural variegation from impurities in the ash that we lost at
cone 1, but at the lower cones it was more controllable. By changing the
formula to 70/30 we fired it to cone 10 reduction. Several students tried
50/50 combinations to fire at cone 06, but we did not explore this area
beyond a few experiments as we needed a low temperature clay body.
Several chemist/ potters have run an analysis on "Insight" and suggested
only that a small percentage of silica be added for strength if it is used
for dense commercial ware.
Over the last 10 years we have made the glaze in large batches, using 60
pounds of ash with 40 pounds of gertsley in a 50 gallon plastic garbage
can. Students then removed the glaze to 5 gallon pails and mixed their own
colors using oxides, stains, and zircopax to taste. It is possible to
measure small batches of test glaze materials using tablespoon, cup or
grams, as long as the basic premise of 60/40 is followed. We had almost
zero failure due to glaze , but as always with students we had failure due
to technique.
The idea or concept of this simple, low tech glaze is ideal for home
potters, beginners, schools, and commercial potters, it is inexpensive,
easy to make, does not settle in storage, and dries on the pots like
cement. Being able to handle the dried glazed pots without chipping, or
powdering is perfect for schools and commercial potters.
This glaze has endless possibilities, it can be dipped, sprayed, brush
applied, thinned, thickened, and colored to endless hues. It can be used
clear, or opaque, it works well over other glazes or in combination with
slips. Students at Hopkins High School in Minnesota have tried just about
every way possible to use and abuse it, but it just keeps working.
SIDEBAR
Larron Lerdall is a full time potter from Mesa, Arizona. He started using
60/40 as his base glaze 10 years ago and has developed a technique of
spraying over tape, stickers, and masked shapes. He has added commercial
colorants to the glaze to develop a rich color palette. He fires both
electric kilns and gas reduction. He has fired 60/40 in wood, salt, soda
ash and heavy reduction with good results. He has developed some amazing
techniques of spraying multiple layers of colored glazes.
FROM MINNETONKA, MINNESOTA, USA
http://www.pclink.com/melpots (website)
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