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Temper (pottery)
A temper is a non-plastic material added to clay to prevent shrinkage and cracking during drying and firing of vessels made from the clay. Tempers may include: *Bone; *Chaff; *Charcoal; *Ground schist; *Wood ash; * Grit; *Sand or crushed sandstone; *Crushed limestone; *Crushed igneous rocks, such as volcanic rock, feldspar, or mica; *Grog; *Plant fiber; * Horse manure (dried and sifted); *Crushed mollusc shells (including fossilized) (see Shell tempering in the Mississippian culture); and *Freshwater sponge spicules. Some clays used to make pottery Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard and durable form. Major types include earthenware, stoneware and ... do not require the addition of tempers. Pure kaolin clay does not require tempering. Some clays are self-tempered, that is, naturally contain enough mica, sand, or sponge spicules th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chaff
Chaff (; ) is the dry, scaly protective casing of the seeds of cereal grains or similar fine, dry, scaly plant material (such as scaly parts of flowers or finely chopped straw). Chaff is indigestible by humans, but livestock can eat it. In agriculture it is used as livestock fodder, or is a waste material ploughed into the soil or burned. Etymology "Chaff" comes from Middle English ''chaf'', from Old English , related to Old High German ''cheva'', "husk". Grain chaff In grasses (including cereals such as rice, barley, oats, and wheat), the ripe seed is surrounded by thin, dry, scaly bracts (called glumes, lemmas and paleas), forming a dry husk (or hull) around the grain. Once it is removed it is often referred to as chaff. In wild cereals and in the primitive domesticated einkorn,Potts, D. T. (1996) ''Mesopotamia Civilization: The Material Foundations'' Cornell University Press. p. 62. . emmer and spelt wheats, the husks enclose each seed tightly. Before the grain c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fiber Crop
Fiber crops are field crops grown for their fibers, which are traditionally used to make paper, cloth, or rope. Fiber crops are characterized by having a large concentration of cellulose, which is what gives them their strength. The fibers may be chemically modified, like in viscose (used to make rayon and cellophane). In recent years, materials scientists have begun exploring further use of these fibers in composite materials. Due to cellulose being the main factor of a plant fiber's strength, this is what scientists are looking to manipulate to create different types of fibers. Fiber crops are generally harvestable after a single growing season, as distinct from trees, which are typically grown for many years before being harvested for such materials as wood pulp fiber or lacebark. In specific circumstances, fiber crops can be superior to wood pulp fiber in terms of technical performance, environmental impact or cost. There are a number of issues regarding the use of fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kaolin Clay
Kaolinite ( ) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is an important industrial mineral. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral sheet of alumina () octahedra. Rocks that are rich in kaolinite are known as kaolin () or china clay. Kaolin is occasionally referred to by the antiquated term lithomarge, from the Ancient Greek ''litho-'' and Latin ''marga'', meaning 'stone of marl'. Presently the name lithomarge can refer to a compacted, massive form of kaolin. The name ''kaolin'' is derived from Gaoling (), a Chinese village near Jingdezhen in southeastern China's Jiangxi Province. The name entered English in 1727 from the French version of the word: , following François Xavier d'Entrecolles's reports on the making of Jingdezhen porcelain. Kaolinite has a low shrink–swell capacity and a low cation-exchange capacity (1–15 meq/100 g). It is a soft, eart ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pottery
Pottery is the process and the products of forming vessels and other objects with clay and other ceramic materials, which are fired at high temperatures to give them a hard and durable form. Major types include earthenware, stoneware and porcelain. The place where such wares are made by a ''potter'' is also called a ''pottery'' (plural "potteries"). The definition of ''pottery'', used by the ASTM International, is "all fired ceramic wares that contain clay when formed, except technical, structural, and refractory products". In art history and archaeology, especially of ancient and prehistoric periods, "pottery" often means vessels only, and sculpted figurines of the same material are called " terracottas". Pottery is one of the oldest human inventions, originating before the Neolithic period, with ceramic objects like the Gravettian culture Venus of Dolní Věstonice figurine discovered in the Czech Republic dating back to 29,000–25,000 BC, and pottery vessels tha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sponge Spicule
Spicules are structural elements found in most sponges. The meshing of many spicules serves as the sponge's skeleton and thus it provides structural support and potentially defense against predators. Sponge spicules are made of calcium carbonate or silica. Large spicules visible to the naked eye are referred to as megascleres, while smaller, microscopic ones are termed microscleres. The composition, size, and shape of spicules are major characters in sponge systematics and taxonomy. Overview Sponges are a species-rich clade of the earliest-diverging (most basal) animals. They are distributed globally, with diverse ecologies and functions, and a record spanning at least the entire Phanerozoic. Most sponges produce skeletons formed by spicules, structural elements that develop in a wide variety of sizes and three dimensional shapes. Among the four sub-clades of Porifera, three (Demospongiae, Hexactinellida, and Homoscleromorpha) produce skeletons of amorphous silica and o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mississippian Culture Pottery
Mississippian culture pottery is the ceramic tradition of the Mississippian culture (800 to 1600 CE) found as artifacts in archaeological sites in the American Midwest and Southeast. It is often characterized by the adoption and use of riverine (or more rarely marine) shell- tempering agents in the clay paste. Shell tempering is one of the hallmarks of Mississippian cultural practices. Analysis of local differences in materials, techniques, forms, and designs is a primary means for archaeologists to learn about the lifeways, religious practices, trade, and interaction among Mississippian peoples. The value of this pottery on the illegal antiquities market has led to extensive looting of sites. Materials and techniques Mississippian culture pottery was made from locally available clay sources, which often gives archaeologists clues as to where a specific example originated. The clay was tempered with an additive to keep it from shrinking and cracking in the drying and firing pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood and DNA remnants. The totality of fossils is known as the ''fossil record''. Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old. Early edition, published online before print. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusc Shell
The mollusc (or molluskOften spelled mollusk shell in the USA; the spelling "mollusc" are preferred by ) shell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater. The ancestral mollusc is thought to have had a shell, but this has subsequently been lost or reduced on some families, such as the squid, octopus, and some smaller groups such as the caudofoveata and solenogastres. Today, over 100,000 living species bear a shell; there is some dispute as to whether these shell-bearing molluscs form a monophyletic group (conchifera) or whether shell-less molluscs are interleaved into their family tree. Malacology, the scientific study of molluscs as living organisms, has a branch devoted to the study of shells, and this is called conchology—although ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Horse Manure
Manure is organic matter that is used as organic fertilizer in agriculture. Most manure consists of animal feces; other sources include compost and green manure. Manures contribute to the fertility of soil by adding organic matter and nutrients, such as nitrogen, that are utilised by bacteria, fungi and other organisms in the soil. Higher organisms then feed on the fungi and bacteria in a chain of life that comprises the soil food web. History According to a Byzantine tradition attributed to Cassianus Bassus pig dung was generally not usable as fertilizer, except for almond trees. Similar views recorded by Columella were unrelated to the Islamic taboos of later centuries, though the medieval Andalusian writer Ibn Bassal and some later writers from Yemen also recorded negative effects of pig dung "burning" plants. Ibn Bassal described a sort of mixed manure with straw or sweeping mixed in as ', implying that was not composed of only manure. The sweepings from hot bath ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Grog (clay)
Grog, also known as firesand and chamotte, is a raw material usually made from crushed and ground potsherds, reintroduced back into crude clay to temper it before making ceramic ware. It has a high percentage of silica and alumina. It is normally available as a powder or chippings, and is an important ingredient in Coade stone. Production It can be produced by firing selected fire clays to high temperature before grinding and screening to specific particle sizes. Another method makes it from pitchers. The particle size distribution is generally coarser in size than the other raw materials used to prepare clay bodies. It tends to be porous and have low density. Properties Grog is composed of 40% minimum alumina, 30% minimum silica, 4% maximum iron(III) oxide, up to 2% calcium oxide and magnesium oxide combined.. Its melting point is approximately . Its boiling point is over . Its water absorption is maximum 7%. Its thermal expansion coefficient is 5.2 mm/m and thermal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schist
Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes or plates. This texture reflects a high content of platy minerals, such as micas, talc, chlorite, or graphite. These are often interleaved with more granular minerals, such as feldspar or quartz. Schist typically forms during regional metamorphism accompanying the process of mountain building ( orogeny) and usually reflects a medium grade of metamorphism. Schist can form from many different kinds of rocks, including sedimentary rocks such as mudstones and igneous rocks such as tuffs. Schist metamorphosed from mudstone is particularly common and is often very rich in mica (a ''mica schist''). Where the type of the original rock (the protolith) is discernible, the schist is usually given a name reflecting its protolith, such as ''sch ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mica
Micas ( ) are a group of silicate minerals whose outstanding physical characteristic is that individual mica crystals can easily be split into extremely thin elastic plates. This characteristic is described as perfect basal cleavage. Mica is common in igneous and metamorphic rock and is occasionally found as small flakes in sedimentary rock. It is particularly prominent in many granites, pegmatites, and schists, and "books" (large individual crystals) of mica several feet across have been found in some pegmatites. Micas are used in products such as drywalls, paints, fillers, especially in parts for automobiles, roofing and shingles, as well as in electronics. The mineral is used in cosmetics and food to add "shimmer" or "frost." Properties and structure The mica group is composed of 37 phyllosilicate minerals. All crystallize in the monoclinic system, with a tendency towards pseudohexagonal crystals, and are similar in structure but vary in chemical composition. Micas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
