Ceramics Monthly dedicated its’ December 2007 issue to sustainability,
and going green is on everyone’s mind these days. The ceramics process
has limits in that regard, but that doesn’t mean we are exempt from
making an effort. The articles in that issue were interesting, but the
solutions involved major projects like building a new kiln, moving to a
landfill or firing in a neutral atmosphere. These solutions can be
impractical for many potters, but the issue prompted me to think of
simple changes that most potters could make to save fuel without major
disruptions to their lives.
One of the easiest ways is minimizing the number of kiln shelves in
each firing. Shelves have a great deal of mass, and heating them up
takes tremendous energy, so bisque firing without shelves (a.k.a.
tumble stacking) will save a lot of energy. If you can’t tumble stack
the entire load, then just try to reduce the number of shelves.
Using thinner shelves also reduces mass, as will exchanging the hard
brick in a gas kiln bag wall with soft insulating fire brick (IFB).
They will still serve the function of the hard brick bag wall, but they
will take less energy to heat up. If you want to go further, consider
eliminating or minimizing the number of bricks in the bag wall. Or,
instead of using whole hard bricks for posts, try using soaps. Anything
that has less mass but still supports the stack will save energy and
time.
With electric kilns, you should make sure your lid fits tightly. Some
lids can rise slightly (up to ¼ inch) during the firing, which wastes a
lot of heat. A number of them have adjustments in the back but I
secured mine with a brick on the edge. In addition, make sure you put
the spies in during the bisque. Potters often leave the spies out
during the initial stages of the firing to allow water vapor and gases
to escape. But, since we fire on automatic, we often forget to put them
back in during the firing.
Learn the dynamics of the firing cycle. If you know what is happening
during the firing cycle you can make adjustments that will save energy.
For example, if you notice little black spots on the side walls of the
pots in the early stages of a bisque firing, this means that all the
water has left the ware and you can safely turn the kiln up without
fear of pots exploding. If you are merely holding the soak for the sake
of tradition, then you are using energy for no reason. Alternatively,
some people hold a mirror in front of the spy holes to see if there is
any condensation. If there is no evidence of moisture, they know that
the water is out and the kiln can be turned up safely.
Eliminate long overnight warm-ups or pre-heats. These are generally
maintained out of fear rather than necessity. Heating the kiln up
overnight to 1300° F and holding it for four hours (until the person
firing arrives in the morning to finish the firing) is a waste of
energy. Most kilns can be started cold in the morning and fired off in
10–12 hours without any problem. Once the water in the glaze coat is
gone, you can heat the pots up relatively quickly. This doesn’t mean
that you have to eliminate the glaze soak or that you cannot slow
things down towards the end, but it does improve the efficiency of the
firing. You can go relatively fast during the initial stages of firing
if the pots have already been bisque fired. I usually reach 1300° F
between the second and third hour.
Understanding the firing cycle can also help you save energy during the
reduction period. Extremely heavy reduction is not always productive.
Of course, sometimes it is necessary for carbon-trapping Shino glazes,
but mainly we over-reduce out of fear that we are not doing enough. It
is basically for our peace of mind. But if we pay attention, we can
fine tune our firings so that we can get the results we want without
wasting fuel.
| Paying attention to our kilns and their settings is another way to
uncover ways to save energy. Most potters like to leave the damper open
halfway (4½ inches) during the warm-up period (below 1550° F) or even all the way open (9 inches). But I noticed that my kiln will oxidize if
the damper is at 2½–3 inches during the glaze cycle. So I surmised
that, during the early stages, it should also oxidize if it is at 3
inches. When I tried this, I knocked about 2 hours off the firing time.
The idea is to keep the maximum amount of heat inside the kiln to heat
up the kiln, shelves and pieces, rather than allowing it to be swept
out of the chimney. The same logic applies to the air flaps on the
burners. Just determine where the kiln oxidizes during the glaze firing
and use those settings during the early stages rather than leaving the
air flaps wide open. I keep the air flaps on my B-3 venturi burners at
three turns open in the early stages of firing.
Do not over stack a kiln. Tradition tells us that a tight stack means a
good firing, but potters push the limit and try to get the most work
possible into a kiln. They stuff it, thinking they are saving energy,
but this is not always true. It is a lot like a clothes dryer; if you
over fill it, it takes longer and sometimes the clothes don’t ever get
dry. You are better off filling it properly and doing two loads. The
same is true with a kiln; if you over stack it you can reduce air flow,
which results in less efficient firings and more pieces that need to be
refired because they don’t reach maturity or just look bad.
Of course, the most obvious way to save energy is to single fire or to
fire to the lowest possible cone. So earthenware potters who single
fire spend the least amount on fuel. Whenever we talk about saving
energy, people suggest that stoneware potters could, or should, move
from cone 10 firings to cone 6 because they would save a lot of energy
by knocking about three hours off the firing time. This is very true,
but it is not as easy to implement as it sounds. This is like saying we
can save energy by walking or riding a bike to work. But cities have
been designed primarily for driving, so if you try walking or riding to
work, it may take hours to get there and you may even get hit by a car.
So, too, with potters who have developed a way of working and a body of
work that they have spent years perfecting. Changing to cone 6 requires
a paradigm shift that may take months or years to perfect, and the
attempt could cost them valuable sales. That solution may not be
feasible for most, but for potters just starting out or those still
studying, perhaps this would be a good time to learn cone 6 gas firing.
If instructors taught cone 6 gas reduction to their pottery students,
then it would be more easily adaptable to their work when they graduate
and start their business. I know quite a few potters who have been out
of school for twenty years and still use the same glazes and firing
methods that they were taught in school. So schools may be the place to
start teaching and applying more energy efficient methods.
Finally, an easy way to save fuel is to buy locally. It is difficult,
if not impossible, for most of us to dig or mix our own clay, so we buy
clay from suppliers. Often the ingredients come from across the globe,
like kaolin from England or New Zealand. Sometime this cannot be helped
because the material provides unique qualities we want, like
translucency. These dry ingredients are shipped to suppliers who mix
the clay with 25–30% water, which is very heavy (8 pounds per gallon).
Buying clay that has been mixed locally will save the energy that it
takes to ship all that water across the country.
These are just a few of the things we can easily do to save fuel
without any major inconveniences. But perhaps the biggest thing we can
do is to make the effort to learn more about the ceramic process. Then,
armed with this new knowledge of oxides, materials, combustion, etc.,
we can apply it to what we are doing and how we are doing it, which
will lead to greater efficiency, fuel savings and hopefully, better
pots!
the author John Britt lives in Bakersville, North Carolina, and is the
author of the book The Complete Guide to High-Fire Glaze: Glazing &
Firing at Cone 10. For more information and to see John’s work, go to www.johnbrittpottery.com.
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