The Porcelain Story
Porcelain was discovered as a ceramic
material in China thousands of years ago. It was often referred
to as white gold by the Europeans when it was first brought to
the courts of kings. Porcelain is basically a mixture of kaolin,
feldspar and silica that is free of other metallic impurities,
especially iron. Porcelain can be fired to a very high
temperature—2400º F and above. This firing temperature is much higher than
those of other
clays such as earthenware or terra cotta. The high temperature
causes the clay to vitrify and become very dense. Therefore, it
is very strong and durable. This is not your mother's bone
china, which is slip cast and fired to the same temperature as
earthenware. Because it fires white, it provides a wonderful
"canvas" for bright colors and/or transparent glazes.
Glazes are a mixture of sand (silica), a feldspar to help it
melt and an oxide to give it color. This mixture is applied to
the surface of the pot and forms a glass when fired. Light
passes through this glass and hits the porcelain beneath. The
white color of the porcelain bounces the light back, and the
colors grab your heart.
Frankly, porcelain is just too hard for most potters to deal with.
It is very hard to throw because it is not as plastic as other
clays. Some people say it is like throwing with butter. It is
very unforgiving during the drying and firing process. The
drying process requires moderate temperature and humidity. If a
pot is not well made, it will crack or even explode during the firing. It is not a clay for beginners. If you see a well-made
porcelain vessel, you know it was made by a very experienced
potter.
Earthenware, terra cotta and even some stoneware are fired in
an electric kiln at temperatures ranging from 1800º F to 2000º
F.
The atmosphere in these kilns is the same as in the air around
you because heat is caused by the electrical resistance in the
wiring. They achieve color through the use of stains or stable
oxides with a strong flux needed to melt the silica. Bright
colors such as orange usually require a lead-based flux and are
not practical for functional ware.
Reduction firing, on the other hand, requires a fuel-fed flame. At Silver
Ridge we use propane. In order to achieve reduction, you add more
fuel than the air in the kiln can burn efficiently. To keep the
flame burning, oxygen molecules are pulled from the glaze. That
is why it is called reduction: you are reducing the oxygen
molecules on the oxides. This is what gives you copper red or
opalescent titanium. In its normal state, copper is the color
of a penny; when it is oxidized it turns green, and when an
oxygen molecule is removed it turns red. Once this molecular
change takes place, the color is there to stay and won’t ever
fade. In addition, the melting temperatures of porcelain and the
glaze are very close (around 2400º F) so that a bond is formed
between the glaze and the porcelain. This is unlike other clays
where the glaze sits on the surface.
As we’ve seen from old Chinese vessels and today’s pieces
from Silver Ridge, reduction firing produces a piece that is beautiful,
functional and, if you don’t drop it, timeless.
Handmade
All pots at Silver Ridge are individually thrown, trimmed,
glazed and fired. Each piece is slightly different, reflecting
the hand of the potter. It is much less expensive and takes very
little skill to mold or jigger a pot. Each piece molded or
jiggered is exactly the same as the next. Many are imported from
Asia. I’ve been throwing for over 20 years, and my skills
continue to improve. Each piece becomes a part of me as I form
the clay on the wheel and add texture or trim a foot. Glazes
used at Silver Ridge have been developed to give the best color
and durability. There are no commercial glazes, decals or
stamped decorations. If you are paying for handmade pottery,
isn’t that what you want?
Who is Lee Marshall?
Lee grew up in Louisville KY, went to Sacred Heart Academy
and worked at Bremner Bisquit Co. while getting an AS in
mechanical engineering. She later obtained a BS in engineering
from Michigan State University and an MBA from Keller Graduate
School in Chicago. She spent 30 years in "Corporate"
as an engineer and executive in the pharmaceutical and medical
device industries. During this time she discovered pottery making.
She made so much pottery she didn’t know what to do with it,
so she did her first art fair. When someone gave her money for
pots she couldn’t give away to friends and family, it opened
her eyes to many possibilities. In the 90’s, Lee realized that she could leave corporate America behind
and devote her time to her passion of making pots. So she spent
2 years searching for property, designing the house and studio,
and using her engineering skills to manage the building project.
Six years ago, Lee established Silver Ridge Pottery on a 10-acre
mountainside just off Chicken Road in the small community of
Pulltight, Tennessee, about an hour east of Nashville. She now produces
porcelain vessels which can be seen at galleries, gift shops and
art fairs all over the United States.
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