Clay Is Full Of Paradoxes

Published Date: 02 Nov 2017

Chapter 1

INTRODUCTION

Clay is full of paradoxes. It is one of the most technically challenging of art media, and yet is used by the children. Potters must be the first group to be withdrawn from food production and to be engaged in a full time profession of production of earthen vessels. Cooking and storage was a specialized task needing a lot of skill and long training. The potter’s wheel was a momentous invention, ranking along with the mastery over fire, as one of those which most influenced the course of human development. The best pieces of pottery bring out in most of us an almost overwhelming desire to touch, caress and hold them. It is one of the most ancient media, made of the stuff of the earth itself, and yet it is also at the forefront of modern materials science. Historically, Clay has been used to create some of the world’s best art. The tiles of Persian mosques, the sculpture of the early dynasties of china, Pre-Colombian figures in Mesoamerica, the jars of Mycenae, from 2000 B.C., are only few of the best contributions of the history (Peterson, 1995). Clay looks and feels very different in each state of making. Pottery making may appear to be a rather simple, uncomplicated series of steps starting with the mixing of suitable clay with water, forming a shape drying, firing and perhaps glazing. These are the basic steps, but as the potter well knows, there are a number of variables which must be taken in to account within each step as well as the interdependency between any one step and all the others.

Background

As there is a decrease in fire wood for conventional cooking, increased price rate of LPG and insufficient availability of LPG has caused the people to seek other efficient and convenient cooking options such as microwave oven, induction cooker etc in semi-urban and developing rural areas of India. Cooking in such new methods require appropriate equipments. The traditional terracotta products are used mainly in the conventional method wood fire cooking. It’s critical to understand and establish the knowledge of the scope of terracotta vessels for cooking in microwave oven. Terracotta pottery is widely manufactured in terracotta red, tints of red, brown, shaded pink colours. Black pottery is less practiced technique and has aesthetically more value in certain markets. According to historical accounts the art of black pottery came from Gujarat. (Ranjan, 2005) The knowledge of developing effective black pottery is not known widely among the artisans. By conducting experiments on black pottery and creatively using it can create a new line of aesthetics to the pottery products and thus a new identity. Shaded pottery with innovative textures, pattern, and colour are the areas to be further explored through this project which does not exist in the current practice of pottery making. These techniques together can be utilized to raise the level of current terracotta market giving new visual identity to value added improved products. This may eventually give rise to new pottery product line with more aesthetic design and artistic values. The project will conduct various experiments restricting to the indigenous ways to develop design intervention which are part of pottery as a craft making and incorporating the same with the microwave friendly terracotta ware developed. Standardizing the process of developing such new range of product can impose immense potential in the future niche market.

Ceramic wares are generally classified as earthen ware, stoneware, china and porcelain (Kenny, 1949). There is no specific point where one class of pottery differs from the other. All the classes of pottery overlap in the nature and properties possessed during the process of making and after making the product and using it.

Scope of Terracotta

Terracotta is a type of earthen ware which comes along with pottery such as stone ware, earthen, China and porcelain. It is clay based ceramic which forms its permanent solid form by heating and subsequent cooling. The word terracotta literally translates to ‘cooked earth’ or ‘baked earth’ in Latin, which express exactly what the material is consisting of. Various properties such as high plasticity, insulating property, porous nature etc helps to serve its purpose in pottery, bricks, containers, art and craft products, architecture etc. It is one of the most ancient media found from the earth and still it used at the forefront of modern material sciences. Terracotta which comes under the category of ceramics refers to all non-metallic, inorganic materials that lend themselves to permanent hardening by high temperatures. Ceramics are more resistant to heat than any other materials on the face of the earth. Ceramics ranges from an increasing array of industrial products such as computer chips, jet engines, components, the nose cones of rockets, electrical insulators, blast furnace lining, and bathroom fixtures (Peterson, 1995). Since terracotta is a poor conductor of temperature and it’s many others favorable nature made it widely use in architectural roofing and construction of walls in the regions where temperature varies to peak level in summer and winter. Thus a consistent room temperature can be maintained reducing the cooling and heating expenses. In India terracotta baked vessels are widely used for traditional wood fired cooking. But today in the newer context where a transition of microwave oven and induction cooking methods are introduced people are not aware, motivated to use these traditional vessels since it is not established authentically to use it as a standard vessel or utensil in new mediums of cooking such as microwave oven. Since terracotta ware are organic and eco-friendly in nature people and market would accept it and would be more preferred to use it. Also culturally Indians used to like the unique taste of food prepared in terracotta. The recent home and lifestyle trend article appeared in the national daily ‘Indian Express ‘says about people’s preference towards a lifestyle where acceptance of the idea of sustainability and organic living are more welcomed like never before. (Varghese, 2013, p.22)

Vessel making history

The story of clay vessels production in India dates back to 6000 BC through the remains found at Western banks of the Indus River. Around 3000 BC wandering tribes settled over this fertile land and happened to be the beginners of ‘Harappa civilization’ leaving behind a rich culture including pottery. Many of the techniques of pottery making of the forms, decorative designs from this period are still being used today. During Vedic period (1500BC-600BC) pottery known as painted ‘Grey ware’ was produced, whose characteristic was its grey colour, obtained through reduction firing. This was followed by the Northern Black Polished Ware of around 400 BC, a highly lustrous pottery developed during the ‘Mouryan period’. Pottery of Gupta period (AD 300-AD 600) was characterized by decorative bricks, tiles and vessels embellished with painting, stamping, incising and moldings. Sometimes during the invasion of Islam in the 11th century, glaze was introduced (and later by the British) in India. Glazing has really penetrated in some of the urban centers in India recently since it required high temperature kilns which were not affordable in India. There is a good source of low-firing clays in almost every village. Throughout India, village, nomad and city dwellers use terracotta pots to carry water long distance from the well and to keep drinking water cooled and clean from the house. A wide variety of vessels for every day house hold use are made with regional variations on design decoration and ethnic preferences for black or red firing. There are separate shapes for carrying on the head, at the waist or by hand, and special size of pot to contain certain measures of rice, oil, milk and curd. Cooking pots also vary in size and shape from open dishes for cooking chapattis to large round bottomed bowls for boiling paddy. Storage pots for water, grains and dried food stuffs vary from region to region, with the variations in their neck width, height, radius, thickness of the body, bottom width etc…

Terracotta and Indian context

People work in clay follow an ancient tradition in which great deal is still new, and still to be done. There is a comparatively more number of potters live and works in India than in any other Country or landmass of comparable size in the world (Huyler, 1996). "India has one million potters, more than any other country on earth, and their clay techniques have handed down for generation" (Perryman, 2000). India is the country with second largest population in the world. The enormous variation in geography and climate embracing tropical, mountain, desert plain and coastal landscapes resulted in a great diversity of ethnic and cultural groups all over the country. Except the developed and developing many large cities, 80% of this vast population lives in rural village communities where culture and traditions have remained without a drastic change for generations till the contemporary time.

Northern Black Polished Ware

The Northern Black Polished Ware culture of the Indian subcontinent is an Iron Age culture of 7th-2nd Century BC succeeding the Painted Grey Ware culture. It peeked from 5th-3rd Century BC coinciding with the late Vedic period and Mouryan Empire (Shaffer, 1993). A fine gray metallic ware with a glossy black surface characteristic of the Iron Age civilization of northern and central India, dating to c 500-100 BC (Adventure of archeology wordsmith, 2013).This period is noticeable because of the similarities with Harappa culture in the utilization of mud, baked bricks and stone in architecture and similar crafts. Northern Black Polished Ware culture has been found among the places in West Bengal and Bangladesh of today. This particular name is misleading, because it is not only found in north India, It is not always black, nor is it necessarily polished. The NBP is a well fired, wheel made deluxe pottery made of well-levigated clay. It’s a fine ware sometimes as thin as 1.5 mm. Apart from black it is also found in other shades and colors. The pottery has a glossy surface. How exactly this was achieved was not certain. (Singh U, 2009). This pottery is somewhat misnamed, as it is found in the south of India, as well as in the north, and is sometimes brown in colour. But typically it has a black, shiny, almost metallic sheen and exactly how it was made remains unexplained. It was first produced in Magadha and reached its most developed form between 500 and 300 BCE, corresponding with the beginning of Buddhism (Dhammika, 2013) One theory is that some ferruginous compound was applied to pots before they were fired, and that the black colour was the result of firing the pots in a reducing condition or reduction firing were the amount of smoke is increased by allowing the oxygen to enter the kiln is minimized. Another view is that the shiny surface was achieved by applying some material such as oil or plant Juice on the pots after they were fired and remaining still hot (Singh, 2009, p.260) yet another study suggests that magnetic iron oxide gave the black pottery effect and glassy look. Shine was the result of application of liquid clay. NBP is usually unpainted and that makes it unique and beautiful.

Future of Potters in India

Potters in rural India have seen little change for generations. Thus the limitations in their tools resulted in high level of manual dexterity and versatility. Consequence of limitation always motivates in result of innovation and encourages producing work which embodies the most economic solution of form and function with producing artifacts of great beauty and spirit. Transition periods are difficult and it may take time for a new aesthetics and product range to emerge from a new technology. It’s time to spend on documenting, experimenting and celebrating the work of the traditional Indian potter before it is over taken, swallowed up on and lost forever

The group of Vessel makers in India produces traditional products whose forms and functions are virtually indistinguishable from those of their predecessors. The idea of living by art or craft is largely a romantic myth in western thoughts, though in current Indian context craftsmen struggles to compete and retain market value of products and earn livelihood becomes a critical question. Craftsmen are not merely a manual worker who shapes matter in to form, they are the carriers and instrumentality of realizing and visualizing the age old practice and highly evolved attributes of creativity. The wide variety of subcultures in which the pottery as a craft practiced resulted in forming numerous unique and vernacular styles of aesthetic expression geographically. Terracotta vessels and sculptors have both sacred and secular use of accountability. Preservation of the potter families and villages in the world is important, or else it is necessary to have the knowledge they still do, or did, exist. "Gradually indigenous crafts will disappear and may be entirely replaced by colorful plastic vessels and images" (Perryman, 2000). Continuous transfer of western design and globalization has brought in to the country western habits and value system which affected existence of Indian craft and art through the crisis occurred in the cultural identity. Industrial Design in India sensitive to the local cultural heritage can create a cultural identity overcoming the imitative, borrowed culture and decaying identity and existence of Indian art and crafts in product design concepts. It is possible through design intervention in documenting traditional and existing knowledge, and dissemination through developing newer products (Das, 2012, p.25). This should be in tune with realizing the availability of local recourses and harmonizing the technology with the practice followed. Craft is an industry in India practiced by huge number of people. With new materials and process many of the crafts which are functional has been replaced with cheaper products that are mass produced in small enterprise. Crafts remains in a neglected area in developing efforts. The traditional craft item must be used in alternative way to keep the traditions alive since these provide for livelihood of traditional craftsmen. If the crafts have to retain its pre-industrialization glory in daily life, the craftsmen may have to update their knowledge and skills to meet the new emerging avenues. This can be attained by accepting and incorporating new methods, tools and techniques which are part of the scientific and technological evolution had by the time. Taking account of existence of craft in the newer context where a number of other factors such as scientific and technological innovations and market trends are changed is important to think for taking it forward. Designer working in the craft sector have to adopt a new learning process and understand relationship between craftsmen, products and culture. Considering the fairly large number of population involved, even a small intervention can impact significantly where large beneficiaries can be benefited compared to developed countries. Industrial design can help in evolving new strategies of design to reach the vast masses. Thus it could play a vital role in innovating products with high market potential which can be made with local skills."A good example can be revitalization of vegetable dyes, terracotta, local toy and doll industry with proper design and marketing inputs can generate large employment potentials in the rural and semi-urban areas" (Das,2012). In the context of globalization multinationals looking for product markets in culturally diverse countries have realized the fact of flawed marketing of forcing international products and to do rather good job by responding to local needs through new product innovation. It is necessary develop products by understanding current and potential needs of society using local materials and processes.

Microwave Oven, Micro wave oven friendly utensils

Microwave oven is a cooking device that can cook or reheat food much faster than a conventional oven. It is often colloquially shortened to microwave. This kitchen appliance heats food by dielectric heating accomplished with microwave type electromagnetic radiation. Microwave oven has become more popular because of it convenience in usage and it cooks in a relatively short time in comparison to other conventional cooking methods. Microwave oven works by using the technology of radio wave. Most microwave ovens use a common wave frequency of around 2.5 Gigahertz (2500Megartz). This range is proved to be most effective in heating the food to get cooked. (Liao S.Y., 1990) Waves in this frequency range have the property that they are absorbed by fat, water, and sugars. Once absorbed they are directly converted into atomic motion-heat. (Brain M, 2013) Also these waves are not absorbed by most plastics, glass or certain ceramics.

Container precautions to use in microwave oven

Specially developed Glass, plastics or selected ceramic ware are considered best for use in microwave. Even though plastics are widely used to use in microwave cooking, all plastic vessels are not microwave friendly. Plastic utensils specifically designed which are microwave friendly come in the market and used others may melt and causes danger. It’s very critical to select appropriate vessels of suitable material to use in microwave. Even though ceramics are used in microwave they are specifically mentioned or refined to make best usable and durable in microwave oven, all ceramics are not possible to use effectively. Containers like polystyrene (such as foam coffee cups and take-out dishes) glass bottles, cans, metal pots, wooden bowls, mugs or ceramic ware with glued-on handles, and plastic storage containers that are not specifically intended for microwave use. Also Glass dishes with metallic gold or silver trims are unsuitable as they may spark when placed in the oven. Metal dishes, pans, thermometers, metal skewers or foil trays may not be used in any oven. The microwave manufacturers always prescribe the user to use only the safe to use microwave labeled Glass, ceramic or plastic containers (USDA, 2013) Ceramics that are not labeled to use microwave safe may reduce the energy efficiency of the oven, or increased amount of metal content in the body of certain ceramic that are not favorable for the oven may hamper the device in the long run. Even though people use or safe to use some of the ceramics like porcelain, they are not used to use terracotta in the microwave. Mainly it is not established or authenticated any ware about the safe usage of terracotta ware. In a country like India terracotta ware will be the most suitable material for using inside microwave in terms of availability, peoples traditional preference for cooking in terracotta ware etc…

Clay Bodies

Clays are found all over the world. In Ceramics and Pottery Practices understanding clay is as important as process of manufacturing it. Different clays have different properties. Residual clay and Sedimentary clay are two basic types of clays. Residual clays found in the same place as the rock from which it is formed. This clay is purer but less plastic than sedimentary clay. Sedimentary clay is clay from silts washed down or blown from higher regions. This clay contains organic materials there for it is more plastic. Earthen ware clays are secondary clays found in nature. These clays contain iron and other mineral impurities. In the raw this clay is red, brown, grey or greenish in colour. When fired the clay could be pink, buff tan, red or brown or even black depending on the condition of firing. These types of clay are collected from river beds, ponds or lakes.

Plasticity of Clay

Plasticity basically refers to how flexible is a clay or clay body is. Any particular clay's plasticity is greatly influenced by the clay's particle size, water content, and aging. To determine the plasticity of a clay make a coil of the clay and then wrap it around the finger. A plastic clay will not crack or break. Non-plastic clays will form in crack.

Determining the plasticity of Clay

The plasticity of clay can be determined by first making a thin rope and coiling it around the finger. If it shows no sign of cracking then the clay is plastic and if there is a little cracking then ageing the clay in a wet condition will make it workable. Basically the test is to work with the clay to determine if it throws without sagging and joins without cracking. While comparing different clay bodies, all samples have to be aged for equal lengths of time. Three weeks in a plastic state is usually adequate for clay to improve appreciably. In this time the finest particles become thoroughly moist, making possibly the slight chemical breakdown caused by the organic matter contained in all clays.

Clay with plasticity Clay without plasticity

Determining the plasticity of Clay.

Earthenware: Earthen ware are usually made from natural clay and fired in kiln in the range of temperature of around 8000 to 11650 Centigrade (Different source mention different temperatures). The body of earthen ware is non-vitreous that is comparatively porous and soft. Some of the earthen ware can’t hold water unless it is glazed outside (Kenny, 1949). Its colour usually ranges from pale yellowish brown, terracotta red and similar dark colors. These pottery wares are sometimes colored with white or other colored slip called ‘engobes’ before glaze or decorations are applied (Peter, 1990) In India mostly practiced pottery are of earthen ware. (Huyler, 1996)

Stoneware: Stone wares prepared either from natural clay directly available from the nature or using the mixture of different clays and other materials as ‘clay bodies’. It is fired to much higher temperature than earthenware (around 12600) It is hard and more vitreous than earthen ware and able to hold water even when unglazed. Not all natural clays can be used to fire at stone ware temperature as it may melt in high temperature. (Kenny, 1949)

Terracotta: Terracotta comes under the category of pottery made with clay and sometimes clay body. When fired around earthen ware temperature it turns red color. These are not usually glazed. Generally known as ‘terracotta’ (Kenny, 1949)

China: There is a little common agreement on the dividing line between china and porcelain. In general the term ‘China’ refers to a type of ware made of a clay body composed of kaolin, ball clay, feldspar and flint plus a flux. The flux may be a natural ingredient or such as talk or a prepared one such as ground glass. (Peter, 1990) China ware can never be made of natural clay alone. It is produced in two or more firing at different temperatures. The colour of the china ware body is usually white. The number of firing required varies according to the decorative elements requires and colors used to get produced on the surface.

Porcelain: Porcelain requires the highest amount of temperature among the other all pottery practiced. It is always made from a specially prepared body composed of kaolin, ball clay, feldspar and flint. This is true porcelain sometimes called ‘hard paste’. Ware made of a body with additional fluxes is sometimes referred to as ‘soft paste’. Porcelain unlike China ware is made in one fire baking, the body and the glaze maturing together at about 13500 centigrade. The product formed finally is extremely hard and vitreous. (Kenny, 1949), (Peter, 1990)

Porcelain was always been something of romance and glamour. It has always held a special place in the thoughts of men from the history (Kenny, 1949). The formula for producing porcelain has kept potters busy for centuries. Whereas terracotta was always celebrated among the people of basic class to the higher in a country like India and has been followed without a break in the tradition. Terracotta has a deep rooted relation with Indian rituals, tradition, culture festival and beliefs.

Clay and Clay Bodies: A clay and clay body are two different things. Clay is natural product as it comes from the earth. A clay body is something which has been made according to formula by mixing different kinds of clays. And sometimes adding other ingredients to achieve the special properties and desired output.

Clay: Clay is chemically hydrous silicate of alumina. Clay is not a single substance but of a mixture of several substances together (Kenny, 1949) Clay contains various impurities while Aluminum Silicate being the chief ingredient of all. These impurities affect the working property of clay. No two clays dug from the ground are exactly alike or with the same properties. All clay poses two properties of plasticity when it is moist and gets hard when it is heated. Pure clay is composed of one part of alumina and two parts silica, plus chemically combined water. Its formula is Al2O3.2SiO2.2H2O. Thus chemically it is called hydrous aluminum silicate. Chemically combined water doesn’t give plasticity to clay. The formula remains the same when the clay is bone dried also.

Types of Clays:

Feldspar: Feldspar is the parent of clay. There was no clay in the beginning of earth. All the clays of today are a product of change, formed by the decomposition of ‘Feldspathic’ rock weathered by air and water during many thousands of years. Feldspar is an important ingredient to the potter used for most glazes and preparing clay bodies. It’s the chief ingredient of granites and many other rocks. Different Feldspar contains different ingredients which include Potash (K2O), Soda (Na2O) or lime (CaO) and some contains several ingredients. During the weathering process, these substances are dissolved out of the feldspar, while alumina and silica remain to form clay. (Kenny, 1949)

Residual Clay: Pure clay is composed of alumina, silica and chemically combined water. But clay in this pure form doesn’t exist (Kenny, 1949). The clay remained in the same spot where it formed is one of its purest forms available. This is called residual clay. Kaolin or China clay is of this type it is coarse in texture, difficult to work with (non-plastic), and highly refractory (highly heat resistant and not readily melts in high temperature). ‘Kaolin’ the residual clay in which its color remains white before and after baking. ‘Kaolin’ is the principal ingredient in china and porcelain. (Kenny, 1949)

Sedimentary Clay: Most of the clays formed where travelled from its origin to very distant places through the carriers of streams, winds, glaciers etc. Such clay is called sedimentary clay. As a result of its transportation it has been ground finer in grain and contains many impurities, hence it’s more plastic and less refractory than residual clay. Its color in natural state may be anything like- blue, green yellow, red, brown, gray or even black. When fired it is usually some shade of red or buff.

Kinds of sedimentary Clays:

Plastic kaolin

Ball Clay

Fire clay

Stone ware clay

Common clay (Kenny, 1949), (Peterson, 1995), (Peter, 1990)

Characteristics of earthen ware

Earthen ware clay is a low temperature firing clay and is not water proof. It has some advantages. It resist sudden change in temperature and is therefore is good for making baking utensils. It has a feeling of lightness, unlike stone ware. The range colors in earthen ware are also wide.

Firing temperature Specifications

The firing temperature of traditional kiln varies depends on many factors. The amount of wood used, type of wood or any other material, climate and atmosphere temperature and humidity level etc… The firing range of earthen ware clay on its own is about 8500C to 11000C. Stone ware clay bodies are fired from 12000C to 13150C. It is vitreous and therefore water proof even when unglazed. Not many clays can be used on their own as they will deform at these temperatures. Therefore it is necessary to mix these clays. The clay should be sufficiently plastic for a potter to be able to throw it on the wheel with minimum shrinkage and to permit vitrification without distortion or deformation.

Porcelain

Porcelain is a high temperature firing clay like stone ware, but more refined. It is composed of feldspar, silica and china clay.

Feldspar Silica China Clay

It is white, dense, completely vitrified and translucent when thin at temperature above 12600C. it is non-plastic and therefore difficult to throw on the wheel.

Porcelain vessels

Recent technological innovations intervened in pottery practices.

As the industry sector have already moved to mechanized, computerized and automated now the traditional manufacturing sector has not much adopted technology interventions. This is one of the threats that faced by traditional craft sectors that it cannot mass manufacture the craft artifacts using mechanized or computerized methods. Many of the crafts are known for its indigenous and vernacular identity which has been passed on by decades of practice from generation to generation. But technology intervention can be done to make the craft sector run smoothly by making the artisans work easier and more convenient. This can be achieved by studying the various crafts keenly and without violating its aesthetical and product values which has been passed and maintained till now. Technological intervention in pottery practice have introduced to make the artisans work easier and to increase the production rate.