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Pottery is a form of ceramic technology, where wet clays are shaped and dried, then fired to harden them and make them waterproof. Unglazed pottery that is fired at temperatures in the 800 to 1200 °C range, which does not vitrify in the kiln but remains slightly porous is often called earthenware or terra cotta. Clay formulated to be fired at higher temperatures, which is partially vitrified is called "stoneware". Fine earthenware with a white tin glaze is known as faience.
The terms "pottery," "earthenware" and "stoneware" are generally used only for relatively easily constructed utensils such as pots, cups, bowls, etc., and for some decorative items. Similar types of ware made from porcelain clays are simply referred to as "porcelain." Complex extremely high-fired ceramics, where the glaze and body fuse completely, are generally referred to as "products of ceramic technology." Ceramic technology is used for items such as electronic parts and Space Shuttle tiles. Pottery is both an ancient and modern technology, in that it uses materials and techniques that are thousands of years old but also takes advantage of more modern innovations in the fields of chemistry and electronics.
A person who makes pottery is generally known as a potter. The potter's most basic tool is the potter's wheel.
Broken pottery in archaeological sites, called potsherds, help identify the resident culture and date the stratum, by the formation style and decoration. The relative chronologies based on pottery are essential for dating the remains of non-literate cultures and help in the dating of some historic cultures as well.
Techniques
Forming techniques There are three basic categories of forming techniques used in pottery - handwork, wheelwork, and slipcasting. It's very common for wheelworked pieces to be finished by handwork techniques. Slipcast pieces tend not to be, as that negates one of the prime advantages of casting.
Handwork methods are the most primitive and individual techniques, where pieces are constructed from hand-rolled coils, slabs, ropes and balls of clay, often joined with a liquid clay slurry. No two pieces of handwork will be exactly the same, so it is not suitable for making precisely matched sets of items e.g. dinnerware. Doing handwork enables the potter to use their imagination to create one-of-a-kind works of art.
The potter's wheel can be used for mass production, although often it is employed to make individual pieces. A ball of clay is placed in the center of a turntable, called the wheel head, which is turned chiefly using foot power (a kick wheel or treadle wheel) or a variable speed electric motor. Oftentimes a disk of plastic, wood, or plaster is affixed to the wheel head and the ball of clay attached to the disk rather than the wheel head so as to facilitate easy removal of the finished piece. This disk is referred to as a bat. The wheel revolves rapidly while the clay is pressed, squeezed and pulled gently into shape. The process of pressuring the clay into a radial symmetry, so that it does not move from side to side as the wheel head rotates is referred to as "centering" the clay - usually the most difficult skill to master for beginning potters.
Wheel work takes a lot of technical ability, but a skilled potter can produce many virtually identical plates, vases or bowls in a day. Because of its nature, wheel work can only be used to initially create items with radial symmetry on a vertical axis. These pieces can then be altered by impressing, bulging, carving, fluting, faceting, incising, and other methods to make them more visually interesting. Often, thrown pieces are further modified by having handles, lids, feet, spouts, and other functional aspects added using the techniques of handworking. Pottery that is thrown on the wheel is often finished in a process known as trimming. The thrown piece is first allowed to dry to the leather-hard state then it is returned to the potter's wheel, usually with the rim down. The piece must be re-centered to allow trimming of the foot of the pot to create a smooth and well-defined surface.
There are two related techniques that improve repeatability of wheelwork. A jigger is a mould that is slowly brought down onto the outside of an object, whilst it is being turned on a wheel. A solid mould is used to form the inside of the piece. Similarly, a jogger is used to shape the inside of a piece, pressing the outside against a solid mold. Although these techniques have been in use since the 18th Century, they are usually considered minor "industrial" methods by modern studio potters. There is contention among potters over whether a "jigged" piece can be considered hand produced.
Slipcasting is probably the easiest technique for mass-production, especially for shapes not easily made on a wheel. A liquid clay slip is poured into plaster moulds and allowed to harden slightly. This slip can be formulated to mature at a variety of temperatures. Once the plaster has absorbed most of the liquid from the outside layer of clay the remaining slip is poured back into the storage tub, and the item is left to dry. Finally the finished item is removed from the mould, "fettled" (trimmed neatly), and allowed to air-dry. This method is commonly used for smaller decorative pieces, such as figurines, which have many intricate details. In the United States, moulds and their slipcast pieces are primarily an industrial product, and are usually called "ceramics" to distinguish them from other pottery.
Decorative and finishing techniques Additives can be worked into moist clay, prior to forming, to produce desired characteristics to the finished ware. Various coarse additives, such as sand and 'grog' (fired clay which has been finely ground) give the final product strength and texture, and contrasting coloured clays and grogs result in patterns. Colourants, usually metal oxides and carbonates, are added singly or in combinations to achieve a desired colour. Combustible particles can be mixed with clay or pressed into the surface to produce texture. Shredded fiberglass can be used as an additive to improve tensile strength in the finished piece. However, the resulting clay contains sharp fibers, is hard to work with and must be carefully handled.
Throughout history, potters have used a mixture of coloured clays as a distinctive decorating technique. In traditional studio pottery in Great Britain, these techniques were known as "agateware." The name is derived from the agate stone, which shows bands of colours. In Japan, various techniques for combining coloured clay on the potter's wheel are jointly known as "neriage." An analogue of marquetry can also be made, by pressing small blocks of coloured clays together, and using the resulting "mosaic" to create distinctive patterns. The Japanese term for this technique is "nerikome." Agateware and the other varieties of "mottled" ware are made by combining two or more colours or varieties of clay into one completed piece. Different colours of clay are lightly kneaded or slapped together before being formed into a vessal or decorative item. This method is most commonly used for handbuilt pieces. Coloured clay can also be added to a base clay after it is centered on the wheel. Although, in principle, any clays can be combined, differing rates of drying/shrinkage and expansion in firing create structural difficulties. It is best to select a light neutral clay body, and then add a colourant to separate portions of the same body. The different coloured clays can then be joined without significant structural problems. Members of commercial clay "families" often have a similar chemical composition and a similar shrinkage rate, and can be used together.
Burnishing, like the metalwork technique of the same name, involves rubbing the surface of the piece with a polished surface (typically wood, steel or stone), to smooth and polish the clay. Finer clays give a smoother and shinier surface than coarser clays, as will allowing the pot to dry more before burnishing, although that risks breakages.
To give a finer surface, or a coloured surface, a thin slurry of clay called slip can be coated onto the leather-dry clay. Slip produced to a specific recipe is sometimes called an "engobe." Slips or engobes can be applied by painting techniques, or the piece can be dipped for a uniform coating. Many pre-historic and historic cultures used slip as the primary decorating material on their ware. Sgraffito involves scratching through a layer of coloured slip to reveal a different colour or the base clay underneath. If done carefully, one colour of slip can be fired, before a second is applied prior to the scratching or incising decoration. Often slips/engobes used in this process have a higher silica content, sometimes approaching a glaze recipe. This is particularly useful if the base clay is not of the desired colour or texture.
Glazing and firing techniques Glazing is the process of coating the piece with a thin layer of a glassy material (often a mix of dolomite, frit, silica/flint, feldspar, sodium borate, clay and whiting plus metal oxides or carbonates). This is important for functional earthenware vessels, which would otherwise be unsuitable for holding liquids due to porosity. Glaze may be applied by dusting it over the clay, spraying, dipping, trailing or brushing on a thin slurry of glaze and water. Brushing tends not to give very even covering, but can be effective with a second coating of a coloured glaze as a decorative technique. With all glazed items, a small part of the item (usually on the base of the piece) must be left unglazed, else it will stick to the kiln during firing.
Glazes can be formulated to melt within the kiln at various temperatures called "cones" and denoted by a small triangle and a number, which run upwards from cone 1 at 1154 °C and backwards with a preceding 0. Cone 06, for example, is a lower temperature than cone 1 at approximately 999 °C. Glazes formulated to melt between cone 09 (~923 °C) and cone 01 (~1137 °C) are often referred to as "low fire", while glazes which melt between around cone 6 (~1222 °C) and cone 12 (~1326 °C) are called "high fire". Those which melt in the intermediate range are called "mid fire". The temperature within the kiln is often identified using small triangular "Pyrometric cones" of carefully formulated chemical mixtures which melt within a specific temperature range and begin to bend slightly - hence the term "cones" being used to denote temperature.
Some clays and glazes are oxygen-sensitive, most notably those containing iron and copper, and will change color depending on the presence of oxygen during the firing. Kilns can either be "oxidized" by opening a port to allow oxygen into the interior or "reduced" by closing off the kiln from outside air to attain colors as desired.
A number of various firing techniques can be used in addition to normal glaze-firing. Most of these involve heating the kiln to a high temperature and then delivering an amount of dry chemical into the kiln's interior. Sulfur is commonly used, as are various salts or ashes. Such substances will stick to pieces within the kiln and melt onto their surfaces, often resulting in a mottled texture which has a distinctive "orange peel" feel. Colors generally depend on what chemical is added to the kiln. These techniques can have very unusual and frequently unexpected results whether used on an unglazed piece or in combination with normal glazing.
Wood firing is another type of firing which involves using wood, rather than gas or electricity as in most modern kilns, to heat the kiln's interior. It is frequently time-consuming, as the kiln must be stoked for as long as a few days, but the pieces which emerge often have characteristic patches of orange color on the clay itself, known as "blushing".
The western adaptation of Raku firing, a traditional Japanese technique, has enjoyed a deal of popularity due to its relative ease. The kiln is heated to a low temperature, usually no higher than cone 06, and then ware is pulled out of the kiln while still hot (using tongs, of course) and smothered in ashes, paper, or woodchips. This can be done in an enclosed container, which allows the supply of oxygen to be cut off and reduction to take place. The finished products of this process are not suitable for functional use, as the clay remains porous and may have some toxic chemicals held within it as a result of burning the surrounding woodchips or paper used to smother it. However, because of the low temperature it is an extremely quick and easy technique to do, and the clay has a distinctive black color.
Production stages
All pottery items go through a series of stages during construction.
- The raw clay is wedged to make its moisture and other particle distribution homogeneous and to remove air bubbles. It is then shaped either by hand or using tools such as a potter's wheel, an extruder, or a slab roller. Water is used to keep the clay flexible during construction and to keep it from cracking.
- Work that is thrown on the wheel often needs to be trimmed or turned to make its thickness uniform and/or to form a foot on the piece. This process is done when the piece has stiffened enough to survive manipulation. This condition is called leather hard.
- The piece is allowed to air dry until it is hard and dry to the touch. At this stage it is known as greenware. Items of greenware are very brittle but they can be handled with care. Greenware items are often sanded with fine grade sandpaper to ensure a smooth finish in the completed item.
- Sometimes the greenware is given a coating of a liquid clay slip. This is most often done to give a coloured base for decoration, other than the colour of the main clay.
- The greenware is often given a preliminary lower range firing in a kiln. Once it has been fired, the clay is known as 'biscuit' ware or bisque.
- Biscuit ware is normally a plain red, white or brown colour depending on which type of clay is used. This is decorated with glaze and then fired again to a higher temperature.
- Some pieces are not bisque-fired before being glazed. These pieces are called once-fired.
History
Palaeolithic Pottery Pottery found in the Japanese islands has been dated, by uncalibrated radiocarbon dating, to around the 11th millennium BC, in the Japanese Palaeolithic at the beginning of the Jomon period. This is the oldest known pottery. In Europe, burnt clay was already known in the late Palaeolithic (Magdalenian) and was used for female figurines, like the "Venus" of Dolni Vestonice, as well as figures of animals.
Neolithic pottery In Palestine, Syria and south-eastern Turkey, the earliest finds of clay pots date from Neolithic times, around the 8th millennium BC (black burnished ware). Before that, clay had been used to make statuettes of humans and animals that were sometimes burned as well. In the preceding Pre-Pottery Neolithic, vessels made of stone, gypsum and burnt lime (vaiselles blanches or white ware) had been used. Sometimes a mixture of clay and lime was used, not very successfully, in the earliest pottery.
Business
Pottery as a business is classified as an industry based on its purpose. It can be
in the manufacturing industry as a earthenware product (NAICS Code
327112) if what is produced is a new product
to be sold. It can be in the arts industry if the pottery is considered
to be a work of art (NAICS Code 711510),
rather than a product.
There are a variety of ways people make money from potting. Some sell their product locally, at trade shows or via the internet. Others sell original patterns or kits they have designed themselves. And, still others teach potting. The best way to learn more about the viabiiity of any of these business models is to participate in Professional Resources, subscribe to magazines that are related to your interests, and read books that give more in-depth information about the business.
Introduction | Books | Magazines | Professional Resources | Related Articles | Sample Business Plans | Start-up Issues
The Basic Guide to Pricing Your Craftwork
Basic formulas for pricing craftwork, retail or wholesale.
The Basic Guide to Selling Arts & Crafts
Step-by-step help on over 150 topics for marketing your home made crafts.
The Basic Guide to Selling Crafts on the Internet
Unravels the mysteries of selling crafts online with clear, step-by-step advice.
Business and Legal Forms for Crafts
A complete set of business and legal forms designed to meet the active craftperson's every need.
The Big Book of Ceramics
A guide to the history, materials, equipment, and techniques of hand-building, molding, throwing,
kiln-firing, and glazing.
The Ceramic Spectrum
A simpified approach to glaze and color development.
Clay and Glazes for the Potter
Revised edition of Daniel Rhodes' seminal book on the fundamentals of ceramic technology,
adding new sections on health hazards, computer calculation programs, increased color
information and expanded photographic images of both historical and contemporary work.
The Complete Potter's Companion
Explains everything from preparation through firing, with stops along the way for
detailed coverage of working on the wheel; coiled, slab, and pinch pots; mold making;
slip casting; and glazing and decorating.
Crafting as a Business
How to develop a thriving retail business.
Crafting for Dollars
Covers every aspect of starting and managing your own craft-based business.
Crafts and Crafts Shows
Good business practice in dealing with customers, pricing, and presentation in the show booth.
The Crafts Business Answer Book & Resource Guide
Answers to questions about starting, marketing, and managing a homebased business
efficiently, legally, and profitably.
Decorating Techiques
Easy to understand written instructions and color photos showing step-by-step approach
to any style and/or method of decorating available.
Hand-Building Techniques
All the suppies and processes associated with the ceramic techinque of hand-building are
explained in this practical volume: the tools and materials, the properties of different clays,
and the basics of using pinching coils, strips, and slabs to model with clay.
Handmade for Profit
Hundreds of secrets to success in selling arts & crafts.
The Kiln Book
Materials, specifications and construction.
Make It Profitable!
The best ideas and information from 80 professionals in various fields of the craft industry.
The Potter's Dictionary of Materials and Techniques
Alphabetical reference that presents the potter with information on the sources and
character of materials, the behavior of clays and glaze minerals during forming and
firing processes, forming methods and glaze construction, together with explanations
of terminology and historical developments.
Publish Your Patterns
How to write, print, and market your designs.
Thrown Pottery Techniques Revealed
The secrets of perfect throwing shown in unique cutaway photography.
Wood-Fired Stoneware and Porcelain
A great resource for potters interested in this alternative style of firing. The book
contains substantial information on kiln design, clays, glazes, stacking, and firing wood kilns.
Your Crafts Business: A Legal Guide
Explains legal principles that protect a crafts business and help it grow. It also
provides practical advice on how to deal with day-to-day problems -- such as dealing
with delinquent payments. The book provides over a dozen tear-out contracts and other
legal forms, plus step-by-step instructions to fill them out.
Introduction | Books | Magazines | Professional Resources | Related Articles | Sample Business Plans | Start-up Issues
American Artist
Widely read and respected resource featuring paintings, drawings and sculptures
of artists in a variety of mediums. A source of inspiration to begining and seasoned artists.
American Craft
Celebrates contemporary craft, focusing on achievements in the craft media.
Ceramics Art and Perception
Substantial articles and regular features on a broad range of ceramics related subjects
with excellent color photographs throughout. Each issue includes articles from around
the world on historical and contemporary topics, functional and sculptural work,
Ceramics Monthly
Articles, information and resources for and about ceramics and pottery.
Ceramics Technical
A bi-annual magazine devoted to research in the field of ceramics that is of interest
to ceramic artists, studio potters and all interested in the furtherance of skills
and the understanding of materials and processes in ceramic art.
Clay Times
Designed to inform ceramic enthusiasts at all levels of the latest developments
in the clay world, while providing useful infornation and techniques.
Fired Arts and Crafts
The ceramist's reference guide during the creating process. Includes projects with
materials lists and directions, color photographs of finished items, detailed patterns,
and drawings when necessary.
Popular Ceramics
Contains how-to articles, with instructions for ceramic projects. Includes ceramic
information, some historical.
Pottery Making Illustrated
A how-to-magazine for potters - professional or amateur, student or instructor. Each issue
contains practical information presented in a well-illustrated format for the beginner to
the intermediate potter.
Sculpture
Covers news and issues related to contemporary sculpture.
