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84-729: Pottery is one of the oldest human inventions , originating before the Neolithic period , with ceramic objects such as the Gravettian culture Venus of Dolní Věstonice figurine discovered in the Czech Republic dating back to 29,000–25,000 BC. However, the earliest known pottery vessels were discovered in Jiangxi , China, which date back to 18,000 BC. Other early Neolithic and pre-Neolithic pottery artifacts have been found, in Jōmon Japan (10,500 BC),

168-560: A basaltic rock in Kivu ( Zaïre ), they noted how the occurrence of kaolinite depended on the "degrée de drainage" of the area involved. A clear distinction was found between areas with good drainage (i.e., areas with a marked difference between wet and dry seasons) and those areas with poor drainage (i.e., perennially swampy areas). Kaolinite was only found in the areas with distinct seasonal alternations between wet and dry. The possible significance of alternating wet and dry conditions on

252-400: A differentiated culture which was earlier thought to be typical Indus Valley civilisation (IVC) culture. Pottery is durable, and fragments, at least, often survive long after artifacts made from less-durable materials have decayed past recognition. Combined with other evidence, the study of pottery artefacts is helpful in the development of theories on the organisation, economic condition and

336-417: A lack of convincing results in their own experiments, La Iglesia and Van Oosterwijk-Gastuche (1978) had to conclude, however, that there were other, still unknown, factors involved in the low-temperature nucleation of kaolinite. Because of the observed very slow crystallization rates of kaolinite from solution at room temperature Fripiat and Herbillon (1971) postulated the existence of high activation energies in

420-414: A layer structure. From the following equation (as given by Gastuche and DeKimpe, 1962) for kaolinite formation it can be seen that five molecules of water must be removed from the reaction for every molecule of kaolinite formed. Field evidence illustrating the importance of the removal of water from the kaolinite reaction has been supplied by Gastuche and DeKimpe (1962). While studying soil formation on

504-458: A locality. The main ingredient of the body is clay . Some different types used for pottery include: It is common for clays and other raw materials to be mixed to produce clay bodies suited to specific purposes. Various mineral processing techniques are often utilised before mixing the raw materials, with comminution being effectively universal for non-clay materials. Examples of non-clay materials include: The production of pottery includes

588-606: A low shrink–swell capacity and a low cation-exchange capacity (1–15 meq/100 g). Rocks that are rich in kaolinite, and halloysite , are known as kaolin ( / ˈ k eɪ . ə l ɪ n / ) or china clay . In many parts of the world kaolin is colored pink-orange-red by iron oxide , giving it a distinct rust hue. Lower concentrations of iron oxide yield the white, yellow, or light orange colors of kaolin. Alternating lighter and darker layers are sometimes found, as at Providence Canyon State Park in Georgia, United States. Kaolin

672-414: A more distant connection between groups, such as trade in the same market or even relatively close settlements. Techniques that require more studied replication (i.e., the selection of clay and the fashioning of clay) may indicate a closer connection between peoples, as these methods are usually only transmissible between potters and those otherwise directly involved in production. Such a relationship requires

756-492: A review on the formation of kaolinite, raised the fundamental question how a disordered material (i.e., the amorphous fraction of tropical soils) could ever be transformed into a corresponding ordered structure. This transformation seems to take place in soils without major changes in the environment, in a relatively short period of time, and at ambient temperature (and pressure ). Low-temperature synthesis of clay minerals (with kaolinite as an example) has several aspects. In

840-581: A rough guide, modern earthenwares are normally fired at temperatures in the range of about 1,000  °C (1,830 °F) to 1,200 °C (2,190 °F); stonewares at between about 1,100 °C (2,010 °F) to 1,300 °C (2,370 °F); and porcelains at between about 1,200 °C (2,190 °F) to 1,400 °C (2,550 °F). Historically, reaching high temperatures was a long-lasting challenge, and earthenware can be fired effectively as low as 600 °C (1,112 °F), achievable in primitive pit firing . The time spent at any particular temperature

924-419: A series of alternations of periodically changing conditions (by definition, taking place in an open system) will bring about the low-temperature formation of more and more of the stable phase kaolinite instead of (ill-defined) amorphous alumino-silicates. In 2009, up to 70% of kaolin was used in the production of paper . Following reduced demand from the paper industry, resulting from both competing minerals and

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1008-544: A tetrahedral ( T ) sheet composed of silicon and oxygen ions bonded to an octahedral ( O ) sheet composed of oxygen, aluminium, and hydroxyl ions. The T sheet is so called because each silicon ion is surrounded by four oxygen ions forming a tetrahedron. The O sheet is so called because each aluminium ion is surrounded by six oxygen or hydroxyl ions arranged at the corners of an octahedron. The two sheets in each layer are strongly bonded together via shared oxygen ions, while layers are bonded via hydrogen bonding between oxygen on

1092-512: A waterproof barrier, and improve its durability. Below are the major types of glazing commonly used in pottery: 1. Glossy Glaze - Produces a shiny, reflective surface. - Highlights intricate patterns and textures. - Often used for decorative purposes. 2. Matte Glaze - Provides a smooth, non-reflective finish. - Suitable for modern and minimalist designs. - Ideal for functional wares like plates and mugs, as it minimizes glare. 3. Transparent Glaze - Can be glossy or matte. - Allows

1176-406: Is Al 2 Si 2 O 5 (OH) 4 , however, in ceramics applications the same formula is typically written in terms of oxides, thus giving Al 2 O 3 ·2SiO 2 ·2H 2 O . Compared with other clay minerals, kaolinite is chemically and structurally simple. It is described as a 1:1 or TO clay mineral because its crystals consist of stacked TO layers. Each TO layer consists of

1260-452: Is a clay mineral , with the chemical composition Al 2 Si 2 O 5 ( OH ) 4 . It is a layered silicate mineral , with one tetrahedral sheet of silica ( SiO 4 ) linked through oxygen atoms to one octahedral sheet of alumina ( AlO 6 ). Kaolinite is a soft, earthy, usually white, mineral (dioctahedral phyllosilicate clay ), produced by the chemical weathering of aluminium silicate minerals like feldspar . It has

1344-401: Is also important, the combination of heat and time is known as heatwork . Kilns can be monitored by pyrometers , thermocouples and pyrometric devices . The atmosphere within a kiln during firing can affect the appearance of the body and glaze. Key to this is the differing colours of the various oxides of iron, such as iron(III) oxide (also known as ferric oxide or Fe 2 O 3 ) which

1428-419: Is an important raw material in many industries and applications. Commercial grades of kaolin are supplied and transported as powder, lumps, semi-dried noodle or slurry . Global production of kaolin in 2021 was estimated to be 45 million tonnes, with a total market value of US $ 4.24 billion. The English name kaolin was borrowed in 1727 from François Xavier d'Entrecolles 's 1712 French reports on

1512-482: Is associated with brown-red colours, whilst iron(II) oxide (also known as ferrous oxide or FeO) is associated with much darker colours, including black. The oxygen concentration in the kiln influences the type, and relative proportions, of these iron oxides in fired the body and glaze: for example, where there is a lack of oxygen during firing the associated carbon monoxide (CO) will readily react with oxygen in Fe 2 O 3 in

1596-501: Is called the "white gold" belt; Sandersville is known as the "Kaolin Capital of the World" due to its abundance of kaolin. In the late 1800s, an active kaolin surface-mining industry existed in the extreme southeast corner of Pennsylvania, near the towns of Landenberg and Kaolin , and in what is present-day White Clay Creek Preserve. The product was brought by train to Newark, Delaware , on

1680-427: Is done, reported and seen. Older examples of any given technology are often found. The locations listed are for the site where the earliest solid evidence has been found, but especially for the earlier inventions, there is little certainty how close that may be to where the invention took place. The Lower Paleolithic period lasted over 3 million years, during which there many human-like species evolved including toward

1764-400: Is important part of archaeology for understanding the archaeological culture of the excavated site by studying the fabric of artifacts, such as their usage, source material composition, decorative pattern, color of patterns, etc. This helps to understand characteristics, sophistication , habits, technology, tools, trade, etc. of the people who made and used the pottery. Carbon dating reveals

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1848-495: Is included under Homo erectus , while Homo rhodesiensis is included under Homo heidelbergensis . During this period the Quaternary glaciation began (about 2.58 million years ago), and continues to today. It has been an ice age , with cycles of 40–100,000 years alternating between long, cold, more glaciated periods, and shorter warmer periods – interglacial episodes. The dawn of Homo sapiens around 300 kya coincides with

1932-425: Is lit and the woman runs around the circumference of the mound touching the burning torch to the dried grass. Some mounds are still being constructed as others are already burning. Pottery may be decorated in many different ways. Some decoration can be done before or after the firing, and may be undertaken before or after glazing. Glaze is a glassy coating on pottery, and reasons to use it include decoration, ensuring

2016-407: Is lost. Above around 400 °C hydroxyl ions (OH ) are lost from the kaolinite crystal structure in the form of water: the material cannot now be plasticised by absorbing water. This is irreversible, as are subsequent transformations; this is referred to as calcination . Endothermic dehydration of kaolinite begins at 550–600 °C producing disordered metakaolin , but continuous hydroxyl loss

2100-425: Is made by heating materials, generally including kaolin , in a kiln to temperatures between 1,200 and 1,400 °C (2,200 and 2,600 °F). This is higher than used for the other types, and achieving these temperatures was a long struggle, as well as realizing what materials were needed. The toughness, strength and translucence of porcelain, relative to other types of pottery, arises mainly from vitrification and

2184-581: Is normally fired below 1200 °C. Because unglazed earthenware is porous, it has limited utility for the storage of liquids or as tableware. However, earthenware has had a continuous history from the Neolithic period to today. It can be made from a wide variety of clays, some of which fire to a buff, brown or black colour, with iron in the constituent minerals resulting in a reddish-brown. Reddish coloured varieties are called terracotta , especially when unglazed or used for sculpture. The development of ceramic glaze made impermeable pottery possible, improving

2268-480: Is not always the case; for example fritware uses no or little clay, so falls outside these groups. Historic pottery of all these types is often grouped as either "fine" wares, relatively expensive and well-made, and following the aesthetic taste of the culture concerned, or alternatively "coarse", "popular", "folk" or "village" wares, mostly undecorated, or simply so, and often less well-made. Cooking in pottery became less popular once metal pots became available, but

2352-551: Is observed up to 900 °C (1,650 °F). Although historically there was much disagreement concerning the nature of the metakaolin phase, extensive research has led to a general consensus that metakaolin is not a simple mixture of amorphous silica ( SiO 2 ) and alumina ( Al 2 O 3 ), but rather a complex amorphous structure that retains some longer-range order (but not strictly crystalline ) due to stacking of its hexagonal layers. Further heating to 925–950 °C converts metakaolin to an aluminium-silicon spinel which

2436-587: Is one of the most common minerals; it is mined, as kaolin, in Australia , Brazil , Bulgaria , China , Czech Republic , France , Germany , India , Iran , Malaysia , South Africa , South Korea , Spain , Tanzania , Thailand , United Kingdom , United States and Vietnam . Mantles of kaolinite are common in Western and Northern Europe. The ages of these mantles are Mesozoic to Early Cenozoic. Kaolinite clay occurs in abundance in soils that have formed from

2520-428: Is placed within the context of linguistic and migratory patterns, it becomes an even more prevalent category of social artifact. As proposed by Olivier P. Gosselain, it is possible to understand ranges of cross-cultural interaction by looking closely at the chaîne opératoire of ceramic production. The methods used to produce pottery in early Sub-Saharan Africa are divisible into three categories: techniques visible to

2604-405: Is shaped by a variety of techniques, which include: Prior to firing, the water in an article needs to be removed. A number of different stages, or conditions of the article, can be identified: Firing produces permanent and irreversible chemical and physical changes in the body. It is only after firing that the article or material is pottery. In lower-fired pottery, the changes include sintering ,

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2688-465: Is sometimes also referred to as a gamma-alumina type structure: Upon calcination above 1050 °C, the spinel phase nucleates and transforms to platelet mullite and highly crystalline cristobalite : Finally, at 1400 °C the "needle" form of mullite appears, offering substantial increases in structural strength and heat resistance. This is a structural but not chemical transformation. See stoneware for more information on this form. Kaolinite

2772-454: Is still used for dishes that benefit from the qualities of pottery cooking, typically slow cooking in an oven, such as biryani , cassoulet , daube , tagine , jollof rice , kedjenou , cazuela and types of baked beans . The earliest forms of pottery were made from clays that were fired at low temperatures, initially in pit-fires or in open bonfires . They were hand formed and undecorated. Earthenware can be fired as low as 600 °C, and

2856-449: Is that the aluminium cations must be hexacoordinated with respect to oxygen (Caillère and Hénin, 1947; Caillère et al., 1953; Hénin and Robichet, 1955 ). Gastuche et al. (1962) and Caillère and Hénin (1962) have concluded that kaolinite can only ever be formed when the aluminium hydroxide is in the form of gibbsite . Otherwise, the precipitate formed will be a "mixed alumino-silicic gel" (as Millot, 1970, p. 343 put it). If it were

2940-400: The "clay matrix" – composed of grains of less than 0.02 mm grains which can be seen using the high-powered microscopes or a scanning electron microscope , and the "clay inclusions" – which are larger grains of clay and could be seen with the naked eye or a low-power binocular microscope. For geologists, fabric analysis means spatial arrangement of minerals in a rock. For Archaeologists,

3024-565: The "fabric analysis" of pottery entails the study of clay matrix and inclusions in the clay body as well as the firing temperature and conditions . Analysis is done to examine the following 3 in detail: The Six fabrics of Kalibangan is a good example of fabric analysis. Body , or clay body, is the material used to form pottery. Thus a potter might prepare, or order from a supplier, such an amount of earthenware body, stoneware body or porcelain body. The compositions of clay bodies varies considerably, and include both prepared and 'as dug';

3108-563: The Espluga Freda area of Spain were enriched with kaolinite from a detrital source due to denudation . Difficulties are encountered when trying to explain kaolinite formation under atmospheric conditions by extrapolation of thermodynamic data from the more successful high-temperature syntheses. La Iglesia and Van Oosterwijk-Gastuche (1978) thought that the conditions under which kaolinite will nucleate can be deduced from stability diagrams, based as they are on dissolution data. Because of

3192-595: The Newark-Pomeroy line, along which can still be seen many open-pit clay mines. The deposits were formed between the late Cretaceous and early Paleogene , about 100 to 45 million years ago, in sediments derived from weathered igneous and metakaolin rocks. Kaolin production in the United States during 2011 was 5.5 million tons. During the Paleocene–Eocene Thermal Maximum sediments deposited in

3276-523: The Russian Far East (14,000 BC), Sub-Saharan Africa (9,400 BC), South America (9,000s–7,000s BC), and the Middle East (7,000s–6,000s BC). Pottery is made by forming a clay body into objects of a desired shape and heating them to high temperatures (600–1600 °C) in a bonfire , pit or kiln , which induces reactions that lead to permanent changes including increasing the strength and rigidity of

3360-416: The silicic acid must be present in concentrations below the maximum solubility of amorphous silica. The principle behind this prerequisite can be found in structural chemistry: "Since the polysilicate ions are not of uniform size, they cannot arrange themselves along with the metal ions into a regular crystal lattice." (Iler, 1955, p. 182 ) The second aspect of the low-temperature synthesis of kaolinite

3444-612: The Upper Paleolithic period. The upper Paleolithic lasted nearly 40,000 years, while research continues to push the beginnings of behavioral modernity earlier into the Middle Paleolithic. Behavioral modernity is characterized by the widespread observation of religious rites, artistic expression and the appearance of tools made for purely intellectual or artistic pursuits. The end of the Last Glacial Period ("ice age") and

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3528-503: The ability of the involved parties to communicate effectively, implying pre-existing norms of contact or a shared language between the two. Thus, the patterns of technical diffusion in pot-making that are visible via archaeological findings also reveal patterns in societal interaction. Chronologies based on pottery are often essential for dating non-literate cultures and are often of help in the dating of historic cultures as well. Trace-element analysis , mostly by neutron activation , allows

3612-452: The age. Sites with similar pottery characteristics have the same culture, those sites which have distinct cultural characteristics but with some overlap are indicative of cultural exchange such as trade or living in vicinity or continuity of habitation, etc. Examples are black and red ware , redware , Sothi-Siswal culture and Painted Grey Ware culture . The six fabrics of Kalibangan is a good example of use of fabric analysis in identifying

3696-597: The beginning of the Holocene around 11.7 ka coincide with the Agricultural Revolution , marking the beginning of the agricultural era, which persisted there until the industrial revolution. During the Neolithic period, lasting 8400 years, stone began to be used for construction, and remained a predominant hard material for toolmaking. Copper and arsenic bronze were developed towards the end of this period, and of course

3780-417: The branches and then grass is piled high to complete the mound. Although the mound contains the pots of many women, who are related through their husbands' extended families, each women is responsible for her own or her immediate family's pots within the mound. When a mound is completed and the ground around has been swept clean of residual combustible material, a senior potter lights the fire. A handful of grass

3864-460: The chemical weathering of rocks in hot, moist climates ; for example in tropical rainforest areas. Comparing soils along a gradient towards progressively cooler or drier climates, the proportion of kaolinite decreases, while the proportion of other clay minerals such as illite (in cooler climates) or smectite (in drier climates) increases. Such climatically related differences in clay mineral content are often used to infer changes in climates in

3948-431: The cultural development of the societies that produced or acquired pottery. The study of pottery may also allow inferences to be drawn about a culture's daily life, religion, social relationships, attitudes towards neighbours, attitudes to their own world and even the way the culture understood the universe. It is valuable to look into pottery as an archaeological record of potential interaction between peoples. When pottery

4032-413: The daily titrations with hydrochloric acid or sodium hydroxide during at least 60 days will have introduced the necessary element of periodicity. Only now the actual role of what has been described as the "aging" ( Alterung ) of amorphous alumino-silicates (as for example Harder, 1978 had noted) can be fully understood. As such, time is not bringing about any change in a closed system at equilibrium; but

4116-479: The duration of firing influences the final characteristics of the ceramic. Thus, the maximum temperature within a kiln is often held constant for a period of time to soak the wares to produce the maturity required in the body of the wares. Kilns may be heated by burning combustible materials, such as wood , coal and gas , or by electricity . The use of microwave energy has been investigated. When used as fuels, coal and wood can introduce smoke, soot and ash into

4200-509: The effect of digital media, in 2016 the market share was reported to be: paper, 36%; ceramics, 31%; paint, 7% and other, 26%. According to the USGS , in 2021 the global production of kaolin was estimated to be around 45 million tonnes. Global production of kaolin by country in 2012 was estimated to be: Some selected typical properties of various ceramic grade kaolins are: Kaolin is generally recognized as safe , but may cause mild irritation of

4284-436: The end of this period, Homo sapiens . The original divergence between humans and chimpanzees occurred 13 ( Mya ), however interbreeding continued until as recently as 4 Ma, with the first species clearly belonging to the human (and not chimpanzee) lineage being Australopithecus anamensis . Some species are controversial among paleoanthropologists, who disagree whether they are species on their own or not. Here Homo ergaster

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4368-459: The eye (decoration, firing and post-firing techniques), techniques related to the materials (selection or processing of clay, etc.), and techniques of molding or fashioning the clay. These three categories can be used to consider the implications of the reoccurrence of a particular sort of pottery in different areas. Generally, the techniques that are easily visible (the first category of those mentioned above) are thus readily imitated, and may indicate

4452-451: The first place the silicic acid to be supplied to the growing crystal must be in a monomeric form, i.e., silica should be present in very dilute solution (Caillère et al., 1957; Caillère and Hénin, 1960; Wey and Siffert, 1962; Millot, 1970 ). In order to prevent the formation of amorphous silica gels precipitating from supersaturated solutions without reacting with the aluminium or magnesium cations to form crystalline silicates ,

4536-430: The following stages: Before being shaped, clay must be prepared. This may include kneading to ensure an even moisture content throughout the body. Air trapped within the clay body needs to be removed, or de-aired, and can be accomplished either by a machine called a vacuum pug or manually by wedging . Wedging can also help produce an even moisture content. Once a clay body has been kneaded and de-aired or wedged, it

4620-481: The foot) is left unglazed or, alternatively, special refractory " spurs " are used as supports. These are removed and discarded after the firing. Some specialised glazing techniques include: Types of Glazing in Pottery. Glazing in pottery is the process of applying a coating or layer of material to ceramics that, when fired, forms a vitreous or glass-like surface. Glazes enhance the aesthetic appeal of pottery, provide

4704-646: The formation of the mineral mullite within the body at these high temperatures. Although porcelain was first made in China , the Chinese traditionally do not recognise it as a distinct category, grouping it with stoneware as "high-fired" ware, opposed to "low-fired" earthenware. This confuses the issue of when it was first made. A degree of translucency and whiteness was achieved by the Tang dynasty (AD 618–906), and considerable quantities were being exported. The modern level of whiteness

4788-443: The former being by far the dominant type for studio and industry. The properties also vary considerably, and include plasticity and mechanical strength before firing; the firing temperature needed to mature them; properties after firing, such as permeability, mechanical strength and colour. There can be regional variations in the properties of raw materials used for pottery, and these can lead to wares that are unique in character to

4872-412: The fusing together of coarser particles in the body at their points of contact with each other. In the case of porcelain, where higher firing-temperatures are used, the physical, chemical and mineralogical properties of the constituents in the body are greatly altered. In all cases, the reason for firing is to permanently harden the wares, and the firing regime must be appropriate to the materials used. As

4956-592: The geological past, where ancient soils have been buried and preserved. In the Institut National pour l'Étude Agronomique au Congo Belge (INEAC) classification system, soils in which the clay fraction is predominantly kaolinite are called kaolisol (from kaolin and soil). In the United States, the main kaolin deposits are found in central Georgia , on a stretch of the Atlantic Seaboard fall line between Augusta and Macon . This area of thirteen counties

5040-457: The glaze. Timeline of historic inventions The timeline of historic inventions is a chronological list of particularly important or significant technological inventions and their inventors , where known. The dates listed in this section refer to the earliest evidence of an invention found and dated by archaeologists (or in a few cases, suggested by indirect evidence). Dates are often approximate and change as more research

5124-417: The item is impermeable to liquids, and minimizing the adherence of pollutants. Glaze may be applied by spraying, dipping, trailing or brushing on an aqueous suspension of the unfired glaze. The colour of a glaze after it has been fired may be significantly different from before firing. To prevent glazed wares sticking to kiln furniture during firing, either a small part of the object being fired (for example,

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5208-431: The kiln which can affect the appearance of unprotected wares. For this reason, wares fired in wood- or coal-fired kilns are often placed in the kiln in saggars , ceramic boxes, to protect them. Modern kilns fuelled by gas or electricity are cleaner and more easily controlled than older wood- or coal-fired kilns and often allow shorter firing times to be used. Niche techniques include: [...] pots are positioned on and amid

5292-575: The late Middle Ages, as European kilns were less efficient, and the right type of clay less common. It remained a speciality of Germany until the Renaissance. Stoneware is very tough and practical, and much of it has always been utilitarian, for the kitchen or storage rather than the table. But "fine" stoneware has been important in China , Japan and the West, and continues to be made. Many utilitarian types have also come to be appreciated as art. Porcelain

5376-405: The low-temperature nucleation of kaolinite. At high temperatures, equilibrium thermodynamic models appear to be satisfactory for the description of kaolinite dissolution and nucleation , because the thermal energy suffices to overcome the energy barriers involved in the nucleation process. The importance of syntheses at ambient temperature and atmospheric pressure towards the understanding of

5460-604: The manufacture of Jingdezhen porcelain . D'Entrecolles was transcribing the Chinese term 高嶺土 , now romanized as gāolǐngtǔ in pinyin , taken from the name of the village of Gaoling ("High Ridge") near Ehu in Fuliang County , now part of Jiangxi Province 's Jingdezhen Prefecture . The area around the village had become the main source of Jingdezhen's kaolin over the course of the Qing dynasty . The mineralogical suffix -ite

5544-415: The mechanism involved in the nucleation of clay minerals lies in overcoming these energy barriers. As indicated by Caillère and Hénin (1960) the processes involved will have to be studied in well-defined experiments, because it is virtually impossible to isolate the factors involved by mere deduction from complex natural physico-chemical systems such as the soil environment. Fripiat and Herbillon (1971), in

5628-424: The object. Much pottery is purely utilitarian, but some can also be regarded as ceramic art . An article can be decorated before or after firing. Pottery is traditionally divided into three types: earthenware , stoneware and porcelain . All three may be glazed and unglazed. All may also be decorated by various techniques. In many examples the group a piece belongs to is immediately visually apparent, but this

5712-441: The only requirement, large amounts of kaolinite could be harvested simply by adding gibbsite powder to a silica solution. Undoubtedly a marked degree of adsorption of the silica in solution by the gibbsite surfaces will take place, but, as stated before, mere adsorption does not create the layer lattice typical of kaolinite crystals. The third aspect is that these two initial components must be incorporated into one mixed crystal with

5796-526: The outer face of the T sheet of one layer and hydroxyl on the outer face of the O sheet of the next layer. A kaolinite layer has no net electrical charge and so there are no large cations (such as calcium, sodium, or potassium) between layers as with most other clay minerals. This accounts for kaolinite's relatively low ion exchange capacity. The close hydrogen bonding between layers also hinders water molecules from infiltrating between layers, accounting for kaolinite's nonswelling character. When moistened,

5880-418: The plates hydrogen bond directly to each other, so that the dried clay is rigid but still fragile. If the clay is moistened again, it will once more become plastic. Kaolinite group clays undergo a series of phase transformations upon thermal treatment in air at atmospheric pressure. High-energy milling of kaolin results in the formation of a mechanochemically amorphized phase similar to metakaolin , although

5964-501: The popularity and practicality of pottery vessels. Decoration has evolved and developed through history. Stoneware is pottery that has been fired in a kiln at a relatively high temperature, from about 1,100 °C to 1,200 °C, and is stronger and non-porous to liquids. The Chinese, who developed stoneware very early on, classify this together with porcelain as high-fired wares. In contrast, stoneware could only be produced in Europe from

6048-432: The properties of this solid are quite different. The high-energy milling process is highly inefficient and consumes a large amount of energy. Below 100 °C, exposure to low humidity air will result in the slow evaporation of any liquid water in the kaolin. At low moisture content the mass can be described leather dry , and at near 0% moisture it is referred to as bone dry . Above 100 °C any remaining free water

6132-417: The raw materials and cause it to be reduced to FeO. An oxygen deficient condition, called a reducing atmosphere, is generated by preventing the complete combustion of the kiln fuel; this is achieved by deliberately restricting the supply of air or by supplying an excess of fuel. Firing pottery can be done using a variety of methods, with a kiln being the usual firing method. Both the maximum temperature and

6216-789: The rest. This is coincident with the complete collapse of the Indus Valley Civilisation . This event is followed by the beginning of the Iron Age. We define the Iron Age as ending in 510 BC for the purposes of this article, even though the typical definition is region-dependent (e.g. 510 BC in Greece, 322 BC in India, 200 BC in China), thus being an 800-year period. Kaolinite Kaolinite ( / ˈ k eɪ . ə l ə ˌ n aɪ t , - l ɪ -/ KAY -ə-lə-nyte, -⁠lih- ; also called kaolin )

6300-413: The role of periodicity becomes convincingly clear. DeKimpe et al. (1961) had used daily additions of alumina (as AlCl 3 ·6 H 2 O ) and silica (in the form of ethyl silicate ) during at least two months. In addition, adjustments of the pH took place every day by way of adding either hydrochloric acid or sodium hydroxide . Such daily additions of Si and Al to the solution in combination with

6384-568: The skin or mucous membranes. Kaolin products may also contain traces of crystalline silica , a known carcinogen if inhaled. In the US, the Occupational Safety and Health Administration (OSHA) has set the legal limit ( permissible exposure limit ) for kaolin exposure in the workplace as 15 mg/m total exposure and 5 mg/m respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set

6468-467: The sources of clay to be accurately identified and the thermoluminescence test can be used to provide an estimate of the date of last firing. Examining sherds from prehistory, scientists learned that during high-temperature firing, iron materials in clay record the state of the Earth's magnetic field at that moment. The "clay body" is also called the "paste" or the "fabric" , which consists of 2 things,

6552-448: The start of the Middle Paleolithic period. Towards the middle of this 250,000-year period, archaic humans such as Neanderthals and Denisovans began to spread out of Africa, joined later by Homo sapiens . Also late in the period, we have increased evidence of long-distance trade, religious rites, and other behavior associated with Behavioral modernity . 50 kya was long regarded as the beginning of behavioral modernity , which defined

6636-421: The tiny platelike crystals of kaolinite acquire a layer of water molecules that cause crystals to adhere to each other and give kaolin clay its cohesiveness. The bonds are weak enough to allow the plates to slip past each other when the clay is being molded, but strong enough to hold the plates in place and allow the molded clay to retain its shape. When the clay is dried, most of the water molecules are removed, and

6720-864: The transition of allophane into kaolinite has been stressed by Tamura and Jackson (1953). The role of alternations between wetting and drying on the formation of kaolinite has also been noted by Moore (1964). Syntheses of kaolinite at high temperatures (more than 100 °C [212 °F]) are relatively well known. There are for example the syntheses of Van Nieuwenberg and Pieters (1929); Noll (1934); Noll (1936); Norton (1939); Roy and Osborn (1954); Roy (1961); Hawkins and Roy (1962); Tomura et al. (1985); Satokawa et al. (1994) and Huertas et al. (1999). Relatively few low-temperature syntheses have become known (cf. Brindley and DeKimpe (1961); DeKimpe (1969); Bogatyrev et al. (1997) ). Laboratory syntheses of kaolinite at room temperature and atmospheric pressure have been described by DeKimpe et al. (1961). From those tests

6804-569: The underlying decoration or texture of the pottery to show through. - Often used over underglaze decorations. 4. Opaque Glaze - Completely covers the surface of the pottery, hiding any underlying texture or decoration. - Useful for creating uniform, bold colors. 5. Celadon Glaze - A translucent glaze, usually in shades of green or blue. - Originated in China and is popular in East Asian ceramics. - Accentuates carved or textured designs beneath

6888-736: The use of many softer materials such as wood, bone, and fibers continued. Domestication spread both in the sense of how many species were domesticated, and how widespread the practice became. The beginning of bronze-smelting coincides with the emergence of the first cities and of writing in the Ancient Near East and the Indus Valley. The Bronze Age starting in Eurasia in the 4th millennia BC and ended, in Eurasia, c.1200 BC. The Late Bronze Age collapse occurs around 1200 BC, extinguishing most Bronze-Age Near Eastern cultures, and significantly weakening

6972-499: Was later added to generalize the name to cover nearly identical minerals from other locations. Kaolinite is also occasionally discussed under the archaic names lithomarge and lithomarga from Latin lithomarga , a combination of litho- ( Ancient Greek : λίθος ， líthos , "stone") and marga (" marl "). In more proper modern use, lithomarge now refers specifically to a compacted and massive form of kaolin. The chemical formula for kaolinite as written in mineralogy

7056-511: Was not reached until much later, in the 14th century. Porcelain was also made in Korea and in Japan from the end of the 16th century, after suitable kaolin was located in those countries. It was not made effectively outside East Asia until the 18th century. The study of pottery can help to provide an insight into past cultures. Fabric analysis (see section below), used to analyse the fabric of pottery ,

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