Carol Marians has been a potter since 1952 when
she discovered clay in a craft course. She proceeded to earn two Ph.Ds.
from MIT, one in Math , the other in Materials Science. Self-trained in
clay, she studied the literature and took workshops with F. Carlton Ball
and Tom Coleman. She has published in Ceramics Monthly and on the web
http://vickihardin.com/articles/index.html She currently is devoting
her time to the study of glaze.
Lili Krakowski started potting in 1949,
graduated from the School for American Craftsmen , R.I.T. in 1953. A
studio potter she has been a frequent contributor to Ceramics Monthly
and Pottery Making Illustrated.
She wrote "A Basic Internet Glaze Course"
published on ClayArt and
The two have teamed up on this project, being
posted under the pseudonym of Ihada Vishun.
MAKING YOUR OWN GLAZES.
"Any new technology, if sufficiently complex, is
magic", wrote Arthur C. Clarke. We might say:
is indistinguishable from sorcery". Or so it might
appear to newcomers who took a first course in pottery.
Potters make their glazes from ground-up rocks,
bought pre-sorted, cleaned, segregated and ground into
powder. The whole process really is an exotic form of cookery.
Grandmother's Putterkuchel was a sublime confection of feather-light pastry laced
with cinnamon and sugar, a pinch of this, a handful of that, poke and prod
as it goes. She never passed on the recipe! We are left to reconstruct
it--basing ourselves on our own knowledge of what flour and butter do, what eggs
do, and so on.
Many masters of the pottery craft work their
glazes in this manner, mixing and blending, baking the result
in the "oven". The baking is called 'firing' by potters, and the oven is
called a 'kiln'. What potters do is rather simple science and
technology. The actual scientists among us take it from there, and work
on such sophisticated projects as designing nose cones
for space ships!
This course intends to teach the basic,
fundamental principals of glaze technology. It deals with the materials, what
they do/don't do, and firing. It deals with glaze faults, their causes and
cures. We suggest you read "Basic Internet Glaze
Course" along with "Glaze Without Fear"
Glaze is a cousin of glass. A principal
difference between the two is that glaze contains alumina, which
contributes to sticking the molten glaze to the pot. Glaze is not essential. Many
beautiful, unglazed clay works have survived for centuries! Many are
being made now! The notion that all clay MUST be glazed is wrong.
We glaze to make an object more cleanable.
Food-related ware, other functional objects, "need" glaze. So do outdoor
objects; bird baths, sun-dials-- as anyone who has tried to keep them
clean can tell you!
We glaze to make pots more beautiful. Glaze
makes pots more appealing to the eye as well as the touch. Many pots are no big
deal in and of themselves, but become magnificent attired in
sumptuous glaze! Most pots--plates, vases, bowls--really are pretty
much the same. It is their decoration, their glazing that sets them apart.
And many splendid potters mainly address the beauty of glaze.
Much of what is said about glaze bypasses
functionality and beauty and focuses on the SKILL of glazing, because great
skill, and knowledge is needed to design glazes, apply, and fire them
well. Reduction and vapor glazes require a masterly
hand. Raku also demands firing and handling skills. Oxidation fire in a
fuel-burning kiln, and neutral fire such as electric kilns give, require less
physical skill, but as much knowledge. The recent addition of digital
controllers to electric kilns allows their heating and cooling to be
manipulated for specific effects.
Glaze is fascinating . Many potters are more
interested in glaze than in clay proper. Neither interest need be exclusive
. Most potters combine both to their satisfaction. (And there have been
cases---of which Gertrude and Otto Natzler probably are the most famous potters
working as a team. One made pots, the other glazes.)
If glaze qua glaze is not for you, stick with
the commercial ones. There are a plenty of excellent, reliable,
well-tested glazes on the market; certainly more than enough to meet common need.
The higher cost per pot is offset by not having to make a major investment
in materials, and space. Learning about glaze, mixing one's own,
experimenting with glazes. Developing recipes takes time and money. We warn
about this because too many dash in without considering the full
measure of what is involved.
The needed glaze materials cost $4 a pound and
up. The materials are costly, and the total investment is large.
You need a fair amount of each material, or the shipping costs
alone will "kill you". Suppliers give "price breaks" for larger
amounts, but the savings are not major ’till one buys a whole 50
lbs bag. Ideally you can fetch what you need from a
nearby supplier. Which still involves time and money. (There are not that
many large suppliers, and the small "local" ones need to pass on their
WHAT YOU NEED TO YOU MAKE YOUR OWN GLAZES
SPACE: A glaze "pantry", " cupboard" , or
"room", takes space. Not just any space. The corner of your
bedroom ideal for exercise equipment will NOT do as glaze space.
Nor will a corner of den or kitchen.
A GLAZE PANTRY MUST BE: very cleanable, draft
and breeze free; NOT a space people need to walk through--as a
hallway would be--well-lit, and (our guess) a minimum of
6 ft x 6 ft floor space. You need an easily washable table, a washable
floor, lots of shelf space. You need a sink and some sort of
water supply. In one of our studios the sink drains into a
bucket, and the water is supplied by bucket. Running water is nice but
not essential. Fifty pound bags of material must be stored in
solid containers such as garbage cans. These will fit under tables, but
are about 20" across. Smaller quantities of material can be kept in coffee
cans, plastic gallon "mayonnaise" jars, or 5 gallon buckets. These
can be obtained free from restaurants, school, hospital or other
cafeterias. The coffee cans are 6"x8" and the jars 6" x 10". So you can figure out the
shelf space you need.
You need a scale. Much discussion of which is
better--digital or regular. It does not matter. The scales sold at
ceramic supply houses are costly. You can find a perfectly good
scale at a baking or kitchen supply store, on the
Internet--or a thrift shop. An old-style baby scale is not great for
tests, but wonderful for weighing out larger batches of
The following applies equally whether you are
working with clay, glaze, the materials, wet or dry --or "simply" cleaning
You must have:
A PROPER RESPIRATOR, bought from your clay
supplier, who will know the right kind. There are respirators just
for dust, others for toxic fumes (such as those from lusters).
While many potters make do with paper dustmasks, the correct
respirators --kept in good condition--are the ones to use.
You need sets of clothes kept entirely for your
pottery work. These should be smooth and easy to wash. Scrub
suits are ideal. Washable shoes--such as garden clogs--that NEVER leave
the glaze room are needed. Remember: your work clothes carry dust, they
should stay IN your work area, being put on and taken off in the room. Ideally
you put the clothes you take off into a plastic bag wet on the inside, or in
a bucket of water for transport to the laundry-room, where the clothes
will be washed by themselves.
You need: diverse plastic containers, scoops,
and permanent waterproof markers. You need buckets and sponges,
note-taking equipment, a calculator but that comes along below.
Shopping List: For starters you want 5lbs of:
Ball clay (In the US Kentucky Ball Clay OM#4 is
But other ball clays are as good.)
Kaolin (China Clay)
and 1 lb of Tin Oxide
Zirconium Opacifier (sold under different
Smaller quantities of the opacifiers are
included as you need all three to really learn their differences in
glaze. Soda spar has been omitted, as have colorants. Nepheline
Syenite will substitute for Soda spar. Colorants are costly
and not needed at the beginning. Cobalt is the most expensive.
Leave colorants out of your original order, and buy them when you
have some glazes "nailed down", and KNOW you really want to
continue in glaze.
You should have 25 lbs of three clay bodies
OTHER THAN THE ONE YOU ARE USING TO MAKE POTS. These are your
controls. It is on these “other” bodies that you double check your
glazes.Application to different bodies also helps in
finding cures for glaze defects.
REALITY CHECK BEFORE YOU READ ANY FURTHER:
Find your space. Figure out what you need to buy
or build. Check the cost of hiring carpenter, plumber, etc. If you are
renting space, get written permission from the landlord for
rebuilding, modification, or installation of your equipment. Remember: the
wiring or plumbing you put into rented space stays behind if you
move. Remember: any damage caused by your rebuilding, installation
etc is your responsibility.
Consult your dealer and figure out material
Check regulations, zoning, fire laws, insurance
before doing anything about a kiln. (Discussed below).