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CHAPTER NINE 
 

Ceramic Clay: Meaning, Preparation and  
Methods of Production 

Chike Cosmas Aghanya & Obianuju Maria Aghanya 

 
Introduction 

Clay is a chief material used in ceramic production 
and as well the backbone of ceramic art. It is an abundant 
natural material that is found all around us, in gardens, 
fields, along riverbanks or roadsides which originated 
from feldspathic rock.  Clay according to Igbinedion 
(1995) is a natural material found in the earth’s crust or 
rock and it is characterized by plasticity when the 
appropriate amount of water is added. It can be defined as 
a heavy, damp, plastic material that sets upon drying and 
can be changed by heat into a hard, waterproof material. 
Clay can also be seen as an earthy raw material known for 
its sticky plastic nature.  It is an earthy material that is soft 
and plastic when wet and very hard and rocklike when 
fired. It contains alumina, silica and water. However, clay 
is classified into two types; they are primary and 
secondary.  
 
Primary Clay 

This can be also called residual clay.  They are clays 
that have not been transported anywhere, which is 
normally seen at the site of its formation.  They are those 
clays formed from parent rock which are found at their 



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site of formation. They are usually white, do not contain 
impurities and are not plastic.  
Example: Koalin 
 
Secondary Clays 

These can be also called sedimentary clays. They are 
those clays that have been moved from their original site 
to elsewhere by wind, flood, ice etc.  This can be also seen 
as clay which has been transported from the site of the 
original parent rock.  These clays can be found on the 
bank of the river, and on roads.  They are earthenware, 
ball clay and stoneware. Secondary clays contain a lot of 
impurities like iron and organic matter which makes them 
vary in colour like brown, black, grey, green etc. They are 
very plastic.  
 
Properties of Clay 

The properties of clay comprise chemical and 
physical characteristics that can be seen to identify clay.  
Chemical properties are Alumina, Silica, Hydrogen & 
Oxygen (Al2O3+2SiO2+2H2O). Physical properties are 
characterized by Plasticity, Shrinkage, Colour, Strength 
and Residue. 
 
Plasticity: This is a property that enables clay to be 
deformed continuously under a force which exceeds a 
certain minimum value and to retain the new shape when 
the deforming force is removed or reduced below a 
certain value. It is also a property that helps clay to bend 



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to any shape or ability to retain any given shape when 
pressure is applied.  
 
Shrinkage simply means the reduction in the size of 
clayware due to the loss of water when exposed to heat.  It 
is also the decrease in the size of clay due to loss of water 
during drying and firing. During drying, water is lost from 
the surface of the clay, and as the water is lost, the clay 
particles come close together; in other words, it shrinks or 
contracts. During firing, some expansion takes place, and 
the porosity increases.  As firing continues the strength of 
the clay is lower and some parts begin to melt thereby 
making the clay fuse together, the body shrinks and the 
porosity drops. All the water lost in both drying and firing 
brought about a reduction in the size of the clay work. 

Colour helps in the classification of various clays 
both at the green stage and fired state (Otimeyin, 2008). 
Some clay appears white like kaolin while some appear 
red, brown, black etc., like ball clay, and earthenware clay. 
The colour of clays is affected by various oxides and 
impurities present.  For example; when clay comes in 
contact with iron oxide and other dead organic matter, the 
colour will be brown.  

Strength is very important in ceramic production 
because clay with high green strength and high fired 
strength will reduce handling breakages at both the green 
state and fired stage.  This is the ability of the wet clay to 
withstand stress when handling. This is determined by the 
plastic nature of the clay. 



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140 
 

The residue remains derived from sieving clay that 
could not pass through a mesh.  These are particles that 
make up the clay.  It comes in contact with clay during 
transportation. It varies in size.  Such residues are 
sandstone, mica, quartz, feldspar, iron minerals etc.  
 
Preparation of Clay 
This can be done manually by two different methods  
a. Dry method  
b. Wet method  
 
Stages of Dry Method 
1. Dry the already-fetched clay under the sun. 
2. Crush or pound with a pestle and mortar into 
smaller particle sizes.  
3. Sieve with mesh to separate bigger particles from 
smaller particles.  
4. Mix the sieved powdered clay with water. 
5. Allow it to stay for some days for a further 
breakdown of clay. 
6. Knead the clay for homogeneity, then store it for 
ageing. 
 
 
 
 
 
 
 



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Plate 1:  Preparation of clay  

 
Stages of Wet Method  
1. Get already dried fetched clay and pour it into a 

sizeable plastic container that contains water.  
2. Leave it for about five to six days to dissolve 

thoroughly. 
3. Turn the clay with a long stick to loosen the 

remaining lumps.  
4. Sieve with mesh by pouring the slurry clay to pass 

through the mesh into the container.  
5. Leave the already sieved clay to settle at the bottom 

of the container for a day.  



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6. Decant the water from the clay and then pour the 
settled clay on a clay bat made with P.O.P. or 
cemented floor. 

7. Depending on the weather, allow it to harden for 
about a week if it's the rainy season, but in the dry 
season, less than a week. 

8. Knead and wedge the clay for homogeneity, then 
store it for ageing.  

 
Modelling Techniques in Ceramics 

Several methods of modelling in ceramic 
production include pinching, slabbing, coiling method, 
scooping, casting and throwing method. 
 
Pinching 

This is one of the oldest and most useful methods 
of production. It involves the palm and thumbs. It can be 
achieved by pressing in hand your thumb in a ball of clay 
on a palm and gradually forming a desired shape. 
 
Slabbing 

The constructive method of building pots and 
sculptures from slabs of clay is a relatively new 
development in ceramics (Charlotte, F.S; John, T, 2003). 
Slabs can be achieved by slamming lumps of clay on a flat 
board guided with wood, after which, use a roller to 
spread out the clay lump and as well maintain even 
thickness with a saw blade.  Mark and cut the shape of 
each part with a knife when it is leather-hard.  Join the 



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already cut-out shapes by fist scratching the surface and 
then applying the slips. Finally, use a saw blade to scrape 
the excess clay and dress the joints in and out. 
Coiling Method  

Coiling is an adaptable method for forming both 
sculpture and pottery, allowing one to achieve almost any 
shape, size or surface (Charlotte, F. Speight, John Toki, 
2003).  This can be achieved by first rolling clay lump on a 
flat surface to get coils, then the coils are placed in coil 
form on already made bases close to each other. Seal them 
together until the desired shape is achieved. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Plate 2:  Coiling method 
 

 
 



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Scoop Method  
This is one of the simplest methods of modelling in 

ceramics. This can be achieved by first modelling a 
particular object in solid then cutting it into two and using 
modelling tools such as a spoon to remove the unwanted 
clay from the inner part of the object to make it lighter. 
Scratch the surfaces of the two parts then apply slips and 
join them together, finally, dress the area so that the mark 
will not show.  
 
Casting Method  

This is a process that involves pouring a casting slip 
into a porous plaster of Paris mould, leaving it for a given 
time for total absorption of water by mould then excess 
slip will be poured out when the required thickness of the 
cast layer is achieved.  When the cast is leather hard, it will 
be removed for proper smoothing and drying.  Unlike clay 
used in throwing, the clay body for casting need not be 
very plastic to avoid excessive shrinkage. 
 
Throwing Method 

This is a process that consists of shaping a mass of 
spinning or twisted clay between the thumbs, fingers and 
palms of the hands.  It is one of the fastest ways of 
producing pottery wares.  Throwing is therefore the first 
or earliest mechanized aid used in the ceramic industry 
(Igbinedion, 1995).  It is also useful in most institutions of 
learning for teaching ceramics. We have two types of 
throwing wheels; kick when and power wheel. There are 



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various operations in throwing a ware. Such operations 
include: 
 
Centring: The first operation in throwing is to centre the 
lump of clay on the revolving wheel head. To avoid 
wobbly results, perfect centring must be achieved.  This 
operation is done by forming a ball of clay, well kneaded 
and wedged, then stamping the lump onto the centre of 
the wheel. With the aid of two palms, the lump is forced 
down, centred and worked into a symmetrical form. In 
doing this, it is essential that water or slip is applied with a 
sponge, so that the clay flows through the hands easily. 
 
 
 
 
 
 
 
 
 

 
 
 
 
 
 

Plate 3:  Centering 
 



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Opening up the Clay: This can be achieved by pressing 
the thumbs down through the centre of the clay, with the 
fingers on the outside of the ware as guides. To get the 
inner bottom diameter correctly, the opening operation 
has to continue.  In this stage, water is also needed but 
excess of it will be removed with a sponge. 
 
 
 
 
 
 
 
 
 
 

 
 
 
 

Plate 4:  Opening up the Clay 

 
Making a draft or Pulling to the desired Shape 
This is drawing the clay up into a cylinder of desired 
height. It can be attained by using both hands, squeezing 
the lower wall between the thumb and fingers and slowly 
putting it upward.  To make the wall thin down, gentle 
pressure should be added by both hands moving from 



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down to up, trimming the rim of the cylinder when the 
thickness is even. 
 
Shaping or forming of the Pots; The shaping can be 
done by using the fingers inside and outside the cylinder 
with both hands.  This operation is very simple if a good 
cylinder is made. 
 
Cutting and Removing of the Pots: This is the use of 
cutting the wire to cut the pot at the base for easy removal 
from the wheel head.  
 
Trimming and Putting the Foot of the Pot: This is 
done when the post is on a leather hard stage so that it 
cannot deform again. With the aid of leather hard clay, the 
thrown pot is centred on the wheel head then spatulas and 
other turning tools are used to trim the edges and put the 
foot.  
 
Pulling and Fixing the Handle: In this stage, the handle 
is pulled out from a lump of clay and it is allowed to be 
leather hard to avoid distortion. Proper fixing is done by 
adding clay slip on the scratched surface of both the 
handle and the pot to ensure firmness. 
 
Kiln Firing  
The main aim of firing wares in ceramics is to change the 
clay from a green stage to a permanent stage (hard and 
rocklike).  It is a process that brings about change in 



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ceramics after forming and decorating work is complete.  
Firing converts ceramic work from weak clay into a strong 
durable crystalline glass-like form. Ceramic work is 
typically fired twice. It is bisque-fired and glaze fired.  
(ceramicartnetwork.org, Dec. 1. 2021).  This history of the 
kiln is the evolution over a long period from simple 
shallow pits into a fixed structure designed to direct and 
contain the heat of the fire (Okonkwo 2006).  

The kiln is a box-shaped structure built to conserve 
heat used in firing ceramics wares.  It can be further 
defined as an insulated refractory box which retains heat 
either by the combustion of some fuels or by the radiant 
heat of the electrically heating elements.  

Modern kilns are built using refractory insulator 
ceramic fibre wool called kaowool that helps to retain heat 
in the chamber.  Such kilns have control buttons for easy 
adjustment during firing.  There are several types of kilns 
which this book will mention some, they are: Electric kiln, 
Downdraft, updraft, muffle, gas kiln, oil kiln, and wood 
kiln. 
 
Bisque Firing  

The goal of bisque firing is to convert greenware to 
a durable, semi-vitrified porous stage where it can be 
safely handled during the glazing and decorating process. 
It also burns out carbonaceous material (organic materials 
in clay, paper, etc).  Before any work can be fired, it must 
be allowed to become completely bone dry larger or 



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thicker pieces of work must be left for a longer time to 
dry.  

The drying process is complete in the initial stage of 
bisque firing known as “water smoking” at about 1000c – 
6000c, chemically combined water escapes as steam.  At 
this stage, vents are allowed to be open for the easy escape 
of steam. It is advisable to proceed slowly in this stage, too 
much haste will cause the steam to push open or explode 
the work.  

This creates a thundering sound in the kiln as a 
result of shattering all the pieces of work in the kiln.  This 
occurs mostly on thicker wall vases.  To ensure that work 
is safe to be heated further, it is pertinent to leave a biscuit 
firing at a low temperature overnight with the kiln vents 
open.   
 
 
 
 
 
 
 
 
 
 
 
 
 

 



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Plate 5: Bisque firing in a kiln. 

Once, the initial firing is 6000c and beyond, it is safe 
to turn up the heating rate, then close all the vents and 
proceed to the final temperature. Finally, the kiln is 
allowed to cool and offload at a very low temperature of 
about 500c. 
 
Glaze firing  

The temperature of glaze firing is determined by the 
glaze and clay body of the fired work. This should be 
started gradually. As the temperature rises to 6000c, the 
rate of climb can be increased and the whole vents will be 
closed.   

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Plate 6: Glaze firing 



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During firing, the glaze fuses with not only itself 

but also with materials on the clay surfaces it lies on. This 
normally occurs in high-fired glaze-like stoneware glazes.  
The effect of heat on a glaze depends on the amount of 
time given to the final firing temperature.  This 
combination of heat and time is called “heat works”.  It 
can be measured accurately by the pyrometric cones.  

Vitrification occurs when the clay and glaze or 
colours come together and fuse.  At the final stage, the 
glaze bubble and craters form as gas escapes and this may 
cause glaze defects called pinholing if it is not allowed to 
settle. But this will not result if the heat in the kiln is 
sustained at a constant temperature called soaking. 
 
 
Evaluation 
1. Explain two types of clay  
2. Outline the methods of modelling with clay.  
3. Define clay 
4. Examine the physical properties of clay  
5. Model a simple object of your choice. 

 
 
 
 
 
 
 



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References 
Charlotte, F.S. & John, T. (2003). Hands in Clay (fifth 

Edition) New York, McGraw Hill 
 
Igbinedion, S.J.E. (1995). Introduction to industrial 

ceramics, Benin City, Uri Publishing Ltd. 
 
Josie, W. (2007). The practical potter: A step-by-step 

handbook, London: Annes Publishing Limited.  
 
Okonkwo, I.E. (2006). The design and construction of 

kerosene firing down draught kiln, MFA Thesis, 
Department of Fine and Applied Arts, University of 
Nigeria, Nsukka. 

 
Otimeyin, P. (2008). Ceramics at a glance, Asaba: Otaba 

Press Limited. 


