TECHNICAL PAPERS #14
UNDERSTANDING THE SMALL-SCALE
CLAY PRODUCTS ENTERPRISE
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Understanding the Small-Scale Clay Products Enterprise
1984, Volunteers in Technical Assistance
This paper is one of a series published by Volunteers in
Assistance to provide an introduction to specific state-of-the-art
technologies of interest to people in developing countries.
The papers are intended to be used as guidelines to help
people choose technologies that are suitable to their
They are not intended to provide construction or
details. People are
urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and
almost entirely by VITA Volunteer technical experts on a
Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.
VITA staff included Leslie Gottschalk
and Maria Giannuzzi as editors, Julie Berman handling
and layout, and Margaret Crouch as project manager.
Miska Petersham, the author of this VITA Technical Paper and
second one, "Understanding Clay Recognition and
worked in the field of ceramics for many years.
He is also a
designer in glass and wood and a wood carver, and has
experience in these fields in developing countries.
Daniel Rhodes and Gerald Rowan are also experts in clay and
Rhodes is a professor emeritus at Alfred University,
New York, in ceramics.
He is the author of four books on
ceramics, and has experience with pottery design, glazes,
molds, clay refining, etc.
Gerald Rowan is the chairman of the
art department at Northampton Community College,
has a wide knowledge of ceramics, clay, brick making, kiln
glazes, owner made equipment, etc.
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries.
information and assistance aimed at helping individuals and
groups to select and implement technologies appropriate to
maintains an international Inquiry Service, a
specialized documentation center, and a computerized roster
volunteer technical consultants; manages long-term field
and publishes a variety of technical manuals and papers.
THE SMALL-SCALE CLAY PRODUCTS ENTERPRISE
VITA Volunteer Miska Petersham
People discovered bow to use clay over 20,000 years
basic principles of shaping, drying, and firing clay are
the same today as they were then.
The only significant changes
since the discovery of clay have been the identification of
additional clay materials and improvements in the methods of
making clay products.
Every age has left behind objects made of clay.
Before the introduction
of plastics and sheet tin, most containers for food--whether
in solid or liquid form--were made of clay or glass.
was also used for architectural decoration as well as
material, for it was plentiful and long lasting.
Although the introduction of new materials and techniques
reduced the use of clay in many areas, clay still plays an
role. It is a
versatile material that can be used at all
levels of technology.
It is common in most parts of the world,
and it is possible to collect and use it for some types of
products without large capital outlays.
Yet, in many developing
countries, it is an underutilized resource.
APPLICATIONS OF CLAY
Ceramics is the general term for manmade products shaped
natural clay material and transformed into a permanent hard
by heat. The term
Pottery and porcelain consisting of such
articles as porcelain
dinnerware, sanitary ware (toilets, sinks,
cookware, and flowerpots. Pottery is
especially earthenware and stoneware, which
primarily to container forms (e.g., pots, vessels)
from low-fired red clay. This
varies greatly from place to place.
are terms used when referring to dinnerware
decorative items such as ashtrays and small sculptures.
Structural and industrial ceramics
consisting of a wide
articles used in building and industry.
sewer pipes are some examples of structural
products. Sparkplugs, insulators,
some industrial ceramics.
ORIGIN AND COMPOSITION OF CLAY
The weathering of igneous rock (rock of volcanic origin)
long stretches of geological time causes the formation of
minerals. This rock
is usually feldspathic (i.e., it contains
mostly feldspar) in temperate areas and on large continental
masses, whereas in tropic volcanic areas where little or no
feldspar exists, it is usually basaltic (i.e., it contains
different geographic locations, source materials,
and climatic (weathering) conditions produce different
of clay minerals and different kinds of impurities which
result in the different working characteristics of the
Most clay is made up of several clay minerals, which are
but have different working characteristics.
Although one cannot
see with the naked eye what clay minerals are present and in
proportion, experienced ceramists usually can guess the
of clays by observing their handling and firing properties.
Determining precisely what minerals are actually present
expensive, careful, and elaborate laboratory analysis--but
this is subject to error.
Kaolin ([A1.sub.2.O.sub.3]/[2SiO.sub.2]/[2H.sub.2.O]) is the
most common clay mineral, but
pure kaolin deposits are a rare find.
These deposits, when found,
often have commercial value because their use in industry is
limited to ceramics.
Pure kaolin is white, non-plastic, and
highly refractory (refractory clays are ones that resist
do not melt when they are subjected to high firing
It is called a primary clay, because it is clay found where
Most clays are predominantly kaolin mixed with other clay
and impurities such as iron, manganese, mica, silica, and
rock fragments. The
different mixes and proportions affect the
working properties of clays, causing them to vary in their
Some clays are suitable for one kind of product only, others
have broader uses, and still others are totally
only sure way to determine the workability of a particular
is to make the desired product on a trial basis and analyze
results. This kind
of practical test is much more satisfactory
for most operations than the more complicated laboratory
which should be undertaken only after a clay or blend is
Red clays are most commonly found in deposits on or near the
surface of the earth.
They are called secondary clays because
they have been eroded and carried from their primary source
frost, rain, or water bodies, to become huge sedimentary
at the bottom of lakes and seas.
As they are borne along, these
clays come into contact with other natural substances, such
sand, calcium, and iron compounds.
Red clays contain various
impurities, which lower the clays' resistance to heat,
them suitable only for earthenware.
Earthenware clay is usually
dark red, very plastic, and fires at a relatively low
Many clays fall between kaolin (the purest clay) and red
(the least pure clay) in their working properties, and each
must be tested individually to determine its
general differences exist between clays found in temperate
and those found in tropical volcanic regions.
are the result of changes in the proportions of clay
and impurities. The
principal differences between the two
clays are outlined in Table 1, generally indicating the
which clay deposits must be examined for suitablility.
1. Reliability of Temperate Clays
Versus Tropical Volcanic Clays
Type of Origin
Clay Mix of Clay
mixed the same
even in one
Although all deposits should be checked carefully for
and content, this holds true especially for clays found in
clays can be used to make some kinds of clay
products, but they are often more difficult to use and
much more skill and care.
II. BASIC TECHNOLOGY
ACQUIRING YOUR CLAY
If you paln to produce large quantities of clay objects, you
should be sure that there is a sufficient reserve of clay of
same quality to last a minimum of 10 years.
The clay should be of
sufficiently high quality to produce the desired
purchasing clay, costs may vary from a few cents to 20 or 30
cents per pound. You
should consider 10 to 15 cents a maximum.
an area where producers must gather and process their own
all associated costs must be taken into account.
Clay can be processed either at a plant designed for one
manufacturer or at a processing plant that serves several
operations. Clay is
mined and its impurities removed;
it is then ground if necessary, bagged, and stored in moist
plastic form or as dry powder called clay flour.
transported impurities from the clay is done either in the
wet or dry state, depending on the original material, amount
needed, costs, and use.
The dried, refined clay is then mixed
with other clays or additives, such as feldspar, to produce
desired clay body (a clay body is the prepared material from
which any ceramic article is made).
As in all industries, the ceramic industry has developed its
clay terminology over the years.
In the sections that follow,
some of the most common terms relating to various clay
are defined. Almost
all of these processes may be done by hand,
by simple foot-powered machines, or by complex mechanically
both the cost and the quality of the
clay product go up as the sophistication in technology
In the case of large-scale mass production of one item, the
per item generally decreases, given that the demand for the
Clay bodies are a mixture of one or more natural clays plus
other materials as feldspar, silica, etc.
Clay bodies are prepared
in a liquid state for slip casting; in a semi-solid state
for plastic forming, and in an almost dry state for dry
Potters shape clay in a number of ways.
Some popular shaping
methods are described below.
Throwing is the act of turning a lump of
on a potter's
wheel. The clay is "thrown"
(shaped) on the
the wheel turns.
Jiggering is a highly mechanical method of
tableware. In this process, a
lump of semi-solid clay is
placed on a
convex plaster bat and turned while a
held against it. As the plaster bat
the clay is
squeezed into shape.
Extrusion involves pressing out a lump of
Pressing involves pressing a lump of semi-solid
Slip casting involves making slip (liquid
clay) and pouring
it into a dry
plaster mold. The plaster absorbs
forming a skin of drier clay on the mold surface.
liquid is poured off, this skin is left, taking
shape as the mold. The clay body is
water to make
slip but this ordinary slip is almost
use due to excessive shrinkage. To make
one or more deflocculants (water softeners)
sodium silicate are added in very small amounts.
decreases the water necessary to make the slip
therefore reduces the shrinkage, which allows
it to be
cast. Many clays are not suitable for
difficulty in achieving deflocculation.
test of the casting properties will tell.
Plastic forming: Before semi-solid (plastic)
clay can be
whatever method, it should be mixed (kneaded)
to obtain an
even consistency and eliminate trapped air.
This can be
done by hand, by foot, or by machine.
new plants, a
mix muller to crush and mix and a vacuum
pug mill to
de-air and prepare clay are used.
Dry pressing requires extremely high
pressures and a
carefully-controlled moisture content.
Because of the
expensive equipment, dry pressing is best suited
III. ESTABLISHING A
CLAY ENTERPRISE: VARIATIONS AND
This section discusses the basic resources required to
various kinds of small-scale ceramic plants.
Before we proceed
with this discussion, it is important to note the following:
Opening and maintaining a small-scale ceramic plant is a
demanding operation that requires a full-time commitment.
People should consider embarking on such a venture only if
are sufficiently trained to make high-quality ceramic
and are capable of designing and building the basic ceramic
equipment necessary for making ceramic goods.
apprenticeship for a ceramist is seven years.
A common error is the notion that anyone can set up a
business and be successful at it after only a few weeks of
Given that ceramic technology is relatively simple, setting
up a ceramic business looks deceptively easy.
Sound advice must
be sought from a qualified ceramic expert in order to
the ceramic industry.
The expert must have broad experience in
ceramic technology, design, and marketing, and must have the
to study the local cultural and economic conditions before
Generally speaking, small-scale ceramic production
from relatively simple technology to more complex technology
demand, markets, and expenses increase.
A SMALL-SCALE BRICK MANUFACTURING PLANT
Unsophisticated brick manufacturing can be done in a small
operated by one or more workers.
Setup costs are very low, but a
nearby clay source and cheap or free fuel are
necessary. Fuel can
be wood scraps, coconut husks, or similar material in
Total costs range from about $1,000 for basic equipment to
$10,000 for some good-quality, imported equipment.
The bricks can be formed in simple wood molds on the ground
no elaborate processing equipment required.
For a more sophisticated
operation, simple hand-operated (lever-type) pressing
are available. This
improves both appearance and quality.
In most cases of small-scale brick manufacture no proper
used. An open
setting called a clamp makes use of the brick that
is to be fired. By
leaving open channels through the clamp, a
path for the heat is provided.
After firing, all or part of the
clamp is dismantled.
Often the walls containing the fire mouths
are left up and all other parts rebuilt after each
firing. It is
rare at this level that a regular pottery kiln is used since
is needlessly expensive and holds a minimum of bricks.
For more sophisticated brick manufacturing, the costs rise
increases in plant productivity and in the quality and
of equipment. The
primary task here is to analyze the market, so
that production capacity can be consistent with demand for
product. Only after
analyzing the market can any determination of
feasibility be made.
This paper does not attempt to provide estimates
on the cost of operating a sophisticated brick manufacturing
plant; to do so would be meaningless, since all aspects of
this type of operation are subject to local variation.
A SMALL-SCALE FLOOR OR ROOF TILE MANUFACTURING PLANT
For a very simple, unsophisticated operation, the cost
building costs) should be about $15,000.
There are so many variables
involved that this cost is at best an approximation for
It is possible to hand-make tile of all kinds
at much lower cost, but these are not as readily accepted on
market as more sophisticated tiles.
An exception is those areas
where the hand tradition is already well established and in
cases the conditions of manufacture will already be well
Basic equipment items and their costs are given in Table 2.
Estimated Equipment Costs for a Small-Scale
or Roof Tile Manufacturing Plant
Press and dies
Miscellaneous small equipment
(*) Costs will vary, depending on quality of equipment and
equipment can often be built locally at considerably
less cost than that for imported equipment.
A SMALL HOLLOWWARE PLANT
The type of hollowware product is the key to setup
ceramics (e.g., china and porcelain) require highly refined
feldspar, and silica, which are expensive.
may be purchased locally, if available, or abroad, in their
refined state; or they may be purchased in their unrefined
and refined at the factory.
The setup costs will vary from operation
to operation, depending on the local set of conditions each
For example, the need to import materials
could drive up the costs.
If ceramic materials are available locally, and do not
extensive processing, or if less than top-quality ware is
product, the setup costs can vary from $25,000 to $100,000,
depending on the type and quantity of products produced, and
whether the equipment is made locally or imported.
A small hollowware plant employing 10 to 15 people would
secure a large market for its products to warrant the
setup costs of refining and processing ceramic
processing equipment alone could cost over $100,000.
Plants already in existence in the Orient and some other
have been set up for much less, but it must be remembered
the tradition, necessary skills, and market acceptance have
there for generations.
In order to set up in an area without this
background, very different conditions may apply.
The costs are
considerably higher since there are many more difficulties
For large-scale production of clay products such as
and giftware, the setup costs can range from $100,000 to
of that magnitude call for a careful analysis
of potential markets.
Specialty ceramics such as sparkplugs, insulators, or
porcelain require a small- to medium-sized, highly
operation, as well as a reliable source of high-quality
feldspar, and silica.
The setup costs are therefore relatively
ADVANCEMENTS IN CERAMICS
Simple ceramic technology was developed long ago by families
guilds who would jealously guard from the public any new
they had made in the field.
For this reason, the field of
ceramics was slow to change.
Only within the past 30 to 40 years
have new ceramic discoveries been made available to the
The public now has access to books and courses providing
with a more open learning environment.
Despite the knowledge that
has been gained thus far, many aspects of ceramics are still
Only through continuing research can we
broaden our understanding of the field to make better
findings spurred by research into high heat-resistant
materials continue to become available.
SIMPLE VERSUS ADVANCED TECHNOLOGIES
The advantages of the basic ceramic technologies over more
technologies are that:
ceramists with only minimal skills can
tile easily because of the simplicity of the
entrepreneurs need to invest only a small
amount of capital;
ceramists can produce ceramic articles from
and sell them
on the domestic market.
The only disadvantage of the basic technologies is that they
low- to medium-quality products rather than top-quality
In order to improve significantly the quality of ceramic
products, entrepreneurs would need to invest in more
equipment, as well as hire more highly trained workers.
so, however, would increase both the initial and the
V. CHOOSING THE
Choosing the size, location, and type of ceramic industry
careful consideration of all the facts.
There is no universal
formula. Each case
must be considered on its own since
there are so many factors to consider.
Even for a very small operation, some kind of feasibility
by a qualified person should be undertaken.
That the person
chosen to perform the study be qualified is important, for
bad advice from a nonexpert can cost more in the long run
than getting sound advice from an expert at the very start.
FACTORS TO CONSIDER IN CHOOSING THE TECHNOLOGY
Domestic Versus Imported
Proper clay machinery is one of the keys to a successful
For example, a simple ball mill capable of handling
batches of clay can be built in-country if a good machine
shop is available.
This type of mill is unsophisticated, however,
and has a relatively short life of about five years.
On the other
hand, it costs about $500 to $1,000 and can be repaired
The other extreme is to buy from the United States or Europe
sophisticated mill, which does essentially the same job as a
Sophisticated ball mills last considerably longer
and require less maintenance, but spare parts are available
abroad only, and initial costs are much greater.
Suppliers of ceramic equipment are located in industrialized
and most of their equipment is built to order.
these suppliers have very small inventories, if any, it may
them as long as one to two years to fill orders for new
but there are few central clearing houses.
The best source
of information for used equipment is any large ceramic
house in any of the industrialized countries.
Equipment manufactured in the United States, Britain, and
is well made, sophisticated, and expensive.
India produces ceramic
equipment that is sturdy, less sophisticated, and much
but shipping and actual arrival of the correct piece of
equipment can be the source of many headaches.
Except for fire brick and setter slabs, which must be
most equipment can be built locally if a qualified machine
In selecting equipment, careful consideration should be
energy requirements; the availability of present and future
sources; and current and future energy costs.
Refined clays can sometimes be imported at reasonable costs,
in most instances the following reasons rule against
Reliance on an imported source could cause
to come to a
halt if, for any reason, that source
Costs to import are usaully somewhat higher
costs are higher).
Importation of clays impedes the selling of
Importation of clays drains money out of the
Importation of refined clays takes business
Answering Important Business Questions
Anyone interested in earning a living from ceramic
it a small-scale, medium-scale, or large-scale
know the answers to the seven sets of basic business
questions provided in this section.
Groups of questions are divided
into the following categories:
market survey, fuel source,
clay source, labor, equipment requirements, product design,
1. What clay products are currently in use?
2. In what volume?
3. What is made locally?
What is imported?
4. What percent of the market does the local product
5. What part of the market can you realistically fill?
6. If a new product is considered, what is the expected
7. Is this a guess?
result of a survey? general
1. Type desired?
(Usually gas, oil, wood, or sawdust; electricity
is expensive as is
the equipment required to produce it.
source and type of
clay affect temperature ranges required to
which in turn greatly affects cost.)
4. Estimate of amount to be used?
5. Transportation (If wood or sawdust)?
1. Availability in proper amount?
(10-year supply minimum)
2. Cost to collect and process?
(Under 15 cents per pound to use)
(Knowledge of test results and pilot products tried)
4. What imports are necessary?
(Should not be more than 20 percent)
5. What to import?
1. Trained locally?
2. Trained overseas?
3. Wage pattern, skilled and semi-skilled?
4. Relative productivity?
(i.e., conversion of nomadic tribesman to factory
6. Cultural consideration (i.e., low-class or caste
sexual bias, etc.)
7. Training allowances?
(Usually six months to one year for general
personnel; and two to six years for foremen,
1. Locally built?
(Possible with competent machine shop)
3. What country? (In
the United States, Britain, Europe, and India,
cost and quality
4. Size and type needed?
(Generally requires expert help)
1. Design quality?
(For successful market penetration, designs--especially
hollowware--must be unique and of high
2. Design source? In
house or outside designer?
1. Retail sales potential?
2. Transportation of raw materials (clay is heavy, and a
needed; it must also be stored for processing and
transportation of finished product?
3. Availability of labor?
5. Access to shipping imports or exports?
6. Fuel source?
7. Pollution of environment?
American Ceramic Society Bulletin
American Ceramic Society
65 Ceramic Drive
Columbus, Ohio 43214 USA
British Ceramic Research Association
Queens Road Penkhull
Stoke-on-Trent, ST4 7LQ
Ceramic Industry and Brick and Clay Record
Cahners Publishing Company, Inc.
1350 E. Touhy Avenue
Des Plains, Illinois 60018 USA
Indian Ceramic Society
Central Glass and Ceramic Research Institute
Indonesia Ceramic Research Institute
J1. Jend. Achmad Yani 392
Bandung, West Java
CERAMIC SUPPLIERS AND MANUFACTURERS
GENERAL AND USED EQUIPMENT
Chambers Brothers Division
805 Lake Street
Kent, Ohio 44240 USA
British Ceramic Plant and Machinery
Weybridge, Surrey, KT13 9JS, UK
Denver Equipment Division
Joy Manufacturing Company
Colorado Springs, Colorado 80903 USA
Globe Trading Company (used equipment)
1801 Atwater Ave.
Detroit, Michigan 48207 USA
International Clay Machinery
of Delaware, Inc.
Wellsville, Ohio 43968 USA
Mohr Machinery Company, Inc. (used equipment)
Dearborn, Michigan 48121 USA
Sub. Gebrueder Netzsch
119 Pickering Way
Exton, Pennsylvania 19341-1393 USA
Via Statale Selica
40026 Imola, ITALY
Takasago Industry Company, Ltd.
Toki-city, Gifu-pref, JAPAN 09-54
A. J. Wahl, Inc.
8961 Central Avenue
Brockton, New York 14716 USA
BALL MILLS AND MIX MULLERS
Paul O. Abbe, Inc.
400 Center Avenue
Little Falls, New Jersey 07424 USA
American Clay Machinery Corporation
1716 Dillion Place, NE
Canton, Ohio 44705 USA
Clearfield Machine Company
Clearfield, Pennsylvania 16830 USA
National Engineering Company
Simpson Mix-Muller Division
20 N. Wacker Drive, Suite 2060
Chicago, Illinois 60606 USA
Stoke-on-Trent, ST4 4ES, UK
BURNERS AND BLOWERS
Muncie, Indiana 47302 USA
Miller Equipment Company
Salisbury, North Carolina 28144 USA
SIEVES AND PARTICLE SIZE REDUCTION
Alpine American Corporation
Natick, Massachusetts 01760 USA
FILTER PRESSES, EXTRUDERS AND PUG MILLS
Edward & Jones, Inc.
Box 128, 563 Eagle Rock Avenue
Roseland, New Jersey 07068 USA
FRH Extruding Machines
Plymouth Locomotive works
Bell and High Streets
Plymouth, Ohio 44865 USA
Haendle, Karl & Soehne
D-713 Muehlacker, WEST GERMANY
Alpine, A.D., Inc.
3051 Fujita Street
Torrance, California 90505 USA
Bickley Furnaces, Inc.
Philadelphia, Pennsylvania 19114 USA
Harrop Industries, Inc.
3470 E. Fifth Avenue
Columbus, Ohio 43219 USA
Heimsoth Keramische Ofen
3200 Hildesheim, WEST GERMANY
165 John L. Dietsch Square
Attleboro Falls, Massachusetts 02763 USA
TILE PRESSES/BRICK AND TILE MACHINERY
1220 Dublin Road
Columbus, Ohio 43216 USA
AC Compacting Presses, Inc.
New Brunswick, New Jersey 08902 USA
Cincinnati, Ohio 45211 USA
J.C. Steele & Sons, Inc.
710 S. Mulberry Street
Statesville, North Carolina 28677 USA
Pioneer Pottery. New York, New
1609 North West Boulevard, Columbus, Ohio
Professional Publications, Inc.
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