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 Pottery Making Introduction
Pottery
is one of the most ancient of crafts and is unique in its blend of the
four elements – earth, air, fire and water. The attraction of this
alchemy and endless possibilities for the potter keeps the craft as alive
and exciting today as it was thousands of years ago.
Origins
Today’s studio potter throwing a bowl on an electric wheel
can trace the origin of the technique back to the hand turned invention of
Egypt in 3000 BC. Up until 500 BC, everywhere in the world, pottery was
earthenware – low temperature ware that was still porous and named after
the earth from which it was made. At the time the Chinese developed the
skill of making stoneware which is a high fired, impervious pottery so
named because of the stone like ring it makes when it is struck.
Clays
There are two main types of clay; earthenware and stoneware.
Both are sold in various colours from white and cream to green and red
(red earthenware clay is well known as terracotta). Some potters prefer to
blend their own clay by adding in ingredients like iron oxide to create
speckles, molochite (ground, fired clay) for strength, or stains to create
artificial colours. At the coolest end of the earthenware range is Raku
and at the hottest end of the stoneware scale is porcelain which becomes
almost translucent when fired.
Clay is supplied in damp solid form, well wrapped to prevent
drying. Before anything is made the clay must be properly prepared and all
the air bubbles removed. This process, called wedging, is not unlike
kneading dough and needs to be done on an absorbent surface to prevent the
clay from sticking. A slab of thick plaster or board covered in stretched
hessian are suitable. Each potter finds the most comfortable style of
wedging for themselves, but the process must be repeated until all the air
bubbles have gone. The lump can be sliced with a cutting wire to check
that no bubbles remain.
Waste clay can be dampened down and this mixture (slurry) is
then dried on a plaster block or bat and used after re-wedging.
 Basic techniques
Pinch pots – As the name implies these are made by pinching
clay between the fingers. A ball of clay is cupped in the palm of the hand
and the shape formed by squeezing the clay upwards and outwards between
the thumb and the fingers on the other hand. No water is necessary but the
result must be of an even thickness because a pot with a thick base and
thin rim may crack when firing. The finished shape can be smoothed off
with a damp sponge.
Coil pots – Clay is rolled on a flat surface into sausages
of an even thickness and coiled around a base of clay. One coil is pressed
on top of the next and the pot built up to the desired size. Coils
overlapping inwards will make a cone and outwards will produce a bowl
shape. It is important that the coils are joined together well or they
will break apart during the firing or drying. The rough coils can be
scraped back for a smooth finish or left ridged for effect.
Slab Pots – These are made with rolled slabs of clay by
scratching the joined edges, brushing them with liquid clay slurry and
fitting the pieces together. The slabs are best prepared by rolling the
clay on an absorbent surface using two wooden battens to support the
rolling pin. This keeps the clay at an even thickness – essential for a
successful pot. The rolled slabs are then left to dry to leather hard,
when they can be cut with a sharp knife and ruler to the required shapes.
With slab building it is important to let the pot dry slowly to allow the
joins to bind securely.
Using a wheel
Making pots on a wheel is called throwing because the clay is
thrown outwards by the force of the rotating wheel head. Perfecting this
technique takes a lot of practise and patience. The essence of throwing is
controlling the moving clay and at the same time moulding it into the
shape required.
There are two types of wheel commonly used – electric and
foot –powered kick wheels. Both originate from the ancient stone or
wooden wheels that were spun by an assistant using feet or a stick to
provide momentum.
The ball of clay is squashed firmly into the centre of the
dry wheel head. Centering the clay is the first essential in throwing. The
hands are always kept wet enough to prevent clay from sticking to them but
not so wet as to allow the clay to slide out.
By keeping the hands firm a dome of clay is made that does
not wobble from side to side. Once the clay has been centered the thumb is
pressed into the middle of the dome and supported at both sides with the
fingers. Then, using the dominant hand to push the clay up from the inside
of the forming pot, the other hand is used to push against the outer side
wall of the pot.
The top of the pot may become uneven and it can be trimmed
while the wheel is turning by using a potter’s needle held steadily
against the soft clay at the desired height. Excess water and loose clay
can be sponged off while the wheel is turning slowly.
The pot is cut off the wheel head by drawing a piece of
cutting wire backwards and forwards under the pot. A splash of water on
the wheel head will then make it possible to slide the thrown piece gently
off, to be put aside to dry.
Turning
When the pot has dried to leather hard it is placed up side
down on the centre of the wheel head and secured with small pieces of soft
clay which can be taken away later. With the wheel turning slowly and a
turning tool held firmly over the base of the pot, excess clay is scraped
away to make a foot or just to even up the thickness of the base.
The pot is now ready for final drying in preparation for the
biscuit firing.
Pottery is never as easy as it looks and beginners must
expect a percentage of failures. However, the disappointments are always
surpassed by the satisfaction of success.
Decoration
Some
decoration is best done before the ‘leatherhard’ stage and others when
the raw clay has dried out completely.
Colour – the most fundamental decoration is to change the colour of the
clay and almost every colour imaginable is made possible by mixing body
stains to the clay. Prepared stains and colours are compounded from raw
pigments (colouring oxides), which can also be used alone to colour the
body clay with more unpredictable results.
Coloured clay can be used for marbling by blending two or more colours
together, for inlays by setting a second colour into another and smoothing
the joins, and in ‘bas relief’ by joining a sculpted addition to the
outside of a pot.
Sculpture and sgraffito – A leather hard pot can be incised, have shapes
cut from it, or have its rim pinched up to a crinkly edge. The surfaces of
a pot can be sculpted to create a three dimensional effect using a sharp
knife or sculpting tools. Texture may be added with almost any object,
from a toothbrush to a pattern stamp.
Another method of decoration is sgraffito, whereby a design is drawn on to
a leather hard pot with a pencil and then scratched on by following the
pattern with a pointed tool. In fact most things are possible as long as
the pot does not dry out too much – a quick spray of water prevents this
from happening.
Burnishing
– A particularly nice effect achieved by polishing the leather hard clay
with the back of a spoon or a very smooth stone. This gives a lovely shine
to the finished pot after firing.
Applying slip – Slip is coloured clay that is added to the body when it
is leather hard. It can be painted on with a brush, trailed on using a
‘slip trailer’, dabbed on with a sponge, stamped on with a template
made to any shape or the whole pot can be slightly dipped in the liquid.
It is also possible to use the sgraffito method os decoration through a
layer of slip that has been previously applied, in order to highlight the
colour of the clay beneath.
Slip needs to be the consistency of single cream and is bought ready made
to match the clay body that is being decorated, although some potters do
make their own by mixing clay with body stains and water.
Biscuit
firing – Biscuit or bisque firing mans heating the finished pots in
preparation for glazing. This first firing dries out and hardens the clay
while leaving it absorbent enough to hold the glaze. The process must be
taken slowly over about ten hours – too fast and the clay explodes. The
kiln is then left to cool slowly before it is opened. This can take up to
24 hours. All the water in the clay evaporates at about 500ºC and as a
result the pots shrink a little during the firing.
Decoration on biscuit ware – When the pots have been fired and cooled
they can be decorated with designs, patterns and pictures using a wide
range of under glaze colours. These are either mineral oxides mixed with
water and painted or sprayed on, or prepared colours which are sold in
tubes, as felt pens or pencils. A transparent glaze is applied once the
colour has dried.
Glaze and Glazing – Glaze is a type of glass that sticks to the clay.
Glaze can be bought ready made or made up from a mixture of silica (to
make it glassy), alumina (to give it body), flux (to make the minerals
melt and blend together), colour and water. Depending on the recipe used
glaze can be glossy and smooth, dry and crackled, buttery or any mixture
the potter chooses.
Different
glazes are necessary for earthenware and stoneware clay as each glaze is
designed to match the body of the pot and the temperature to which it is
to be fired. Colours in earthenware glazes tend to be stronger than in
stoneware.
Only the imagination limits the possibilities for glaze decoration.
Sponging, dabbing, spattering with the bristles of a stiff brush are all
possible. Pots can be dipped completely or partly in glaze, liquid glaze
can be poured over them, glaze can be applied with a brush or trailed over
the surface using the same technique as slip trailing, or it can be
sprayed on using a house plant sprayer or spray gun. Areas can even be
masked out with paper or wax or leave them unglazed.
Glaze firing – Pots ready for glaze firing are placed in the kiln on
shelves which are then seperated by props that support another shelve
above. The bottom of the pots must be wiped clean of glaze where they will
come into contact with the shelves, or they will stick. For the same
reason pots must not touch each other and space is also left beside the
kiln walls to allow the heat to circulate.
Once
packed and closed the kiln can then be fired to the desired temperature as
quickly as possible. Unlike biscuit firing there is no risk to the pots
cracking from being fired too quickly. However, there is a possibility
that they will crack if they are cooled too suddenly.
Some glazes, particularly stoneware ones, can be unpredictable and it
doesn’t pay for a beginner to become too attached to a pot prior to
firing until they have mastered as many variables as possible.
Raku
– The kiln used for Raku is usually simple, consisting of a small
chamber made from fire bricks or a steel drum lined with ceramic fibre,
with an inlet for air, a gas burner at the base and a moveable lid that
can act as a flue as well as aiding quick unpacking. From putting the
glazed pot in the kiln to holding the finished product can take as little
as an hour.
The
clay used is course and porous, in fac even after firing the pot remains
porous. The pot is made and biscuit fired in the usual way and then glazed
with a Raku glaze which consists of a lead substitute, a small amount of
clay and colour.
The kiln is preheated until it is glowing with an orange red heat and the
pot is placed inside, the optimum temperature is reached when the glaze
appears glossy all over. Once the pot has been removed it is plunged into
a bed of sawdust and shavings and covered to prevent the wood chips from
bursting into flames. After about ten minutes the pot is lowered slowly
into a container of water where it boils and seethes. A few minutes later
the finished pot is scoured of its sawdust coating to reveal an object
that bears all the marks of the forging and alchemy that it has just
endured.
Anyone
who participates in Raku firing and is prepared to endure the heat, smoke,
and smell and the inevitable failure of imperfection and cracked pots that
sometimes occur, cannot help but be excited by it and perhaps hooked on
pottery for life.
Courses
If you offer pottery courses / evening classes /
demonstrations - please contact us
to advertise your details here.
There are lots of books available to learn the skills from
home.
To
learn proper pottery throwing techniques the best starting point is to
contact polytechnics / colleges to see if they have any organized courses.
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