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Eraser 7-inch
An eraser (also known as a rubber in some Commonwealth countries, including South Africa from the material first used) is an article of stationery that is used for removing marks from paper or skin (e.g. parchment or vellum). Erasers have a rubbery consistency and come in a variety of shapes, sizes and colors. Some pencils have an eraser on one end. Less expensive erasers are made from synthetic rubber and synthetic soy-based gum, but more expensive or specialized erasers are made from vinyl, plastic, or gum-like materials. At first, erasers were invented to erase mistakes made with a pencil; later, more abrasive ink erasers were introduced. The term is also used for things that remove marks from chalkboards and whiteboards. History Before rubber erasers used today, tablets of wax were used to erase lead or charcoal marks from paper. Bits of rough stone such as sandstone or pumice were used to remove small errors from parchment or papyrus documents written ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blackboard
A blackboard (also known as a chalkboard) is a reusable writing surface on which text or drawings are made with sticks of calcium sulphate or calcium carbonate, known, when used for this purpose, as chalk. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone. Design A blackboard can simply be a board painted with a dark matte paint (usually black, occasionally dark green). Matte black plastic sign material (known as closed-cell PVC foamboard) is also used to create custom chalkboard art. Blackboards on an A-frame are used by restaurants and bars to advertise daily specials. A more modern variation consists of a coiled sheet of plastic drawn across two parallel rollers, which can be scrolled to create additional writing space while saving what has been written. The highest grade blackboards are made of a rougher version porcelain enamelled steel (black, green, blue or sometimes other colours). Porcelain is very hard wearing, and blackboar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hymen Lipman
Hymen L. Lipman (March 20, 1817 – November 4, 1893) is credited with registering the first patent for a pencil with an attached eraser on March 30, 1858 (). Hymen L. Lipman was born March 20, 1817, in Kingston, Jamaica, to English parents. He immigrated to the United States around 1829 with them, arriving in Philadelphia, Pennsylvania, where he resided for the remainder of his life. In 1840, Lipman succeeded Samuel M. Stewart, then the leading stationer in Philadelphia. Three years later, he started the first envelope company in the U.S. In August 7, 1848, he was married to Mary A. Lehman, daughter of Peter Lehman, one of the founders of the Philadelphia College of Pharmacy in Philadelphia. They had a son and two daughters. In 1862, Lipman sold his lead-pencil and eraser patent for $100,000 to Joseph Reckendorfer, who went to sue the pencil manufacturer Faber for infringement. In 1875, the Supreme Court of the United States ruled against Reckendorfer, declaring the patent i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curing (chemistry)
Curing is a chemical process employed in polymer chemistry and process engineering that produces the toughening or hardening of a polymer material by cross-linking of polymer chains. Even if it is strongly associated with the production of thermosetting polymers, the term "curing" can be used for all the processes where a solid product is obtained from a liquid solution, such as with PVC plastisols. Curing process During the curing process, single monomers and oligomers, mixed with or without a curing agent, react to form a tridimensional polymeric network. In the very first part of the reaction branches of molecules with various architectures are formed, and their molecular weight increases in time with the extent of the reaction until the network size is equal to the size of the system. The system has lost its solubility and its viscosity tends to infinite. The remaining molecules start to coexist with the macroscopic network until they react with the network creating other c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vulcanization
Vulcanization (British: Vulcanisation) is a range of processes for hardening rubbers. The term originally referred exclusively to the treatment of natural rubber with sulfur, which remains the most common practice. It has also grown to include the hardening of other (synthetic) rubbers via various means. Examples include silicone rubber via room temperature vulcanizing and chloroprene rubber (neoprene) using metal oxides. Vulcanization can be defined as the curing of elastomers, with the terms 'vulcanization' and 'curing' sometimes used interchangeably in this context. It works by forming cross-links between sections of polymer chain which results in increased rigidity and durability, as well as other changes in the mechanical and electrical properties of the material. Vulcanization, in common with the curing of other thermosetting polymers, is generally irreversible. The word vulcanization is derived from Vulcan, the Roman god of fire and forge. History Rubber—latex†... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charles Goodyear
Charles Goodyear (December 29, 1800 – July 1, 1860) was an American self-taught chemist and manufacturing engineer who developed vulcanized rubber, for which he received patent number 3633 from the United States Patent Office on June 15, 1844. Goodyear is credited with inventing the chemical process to create and manufacture pliable, waterproof, moldable rubber. Goodyear's discovery of the vulcanization process followed five years of searching for a more stable rubber and stumbling upon the effectiveness of heating after Thomas Hancock. His discovery initiated decades of successful rubber manufacturing in the Lower Naugatuck Valley in Connecticut, as rubber was adopted to multiple applications, including footwear and tires. The Goodyear Tire and Rubber Company is named after him. Early life Charles Goodyear was born on 29 December 1800, in New Haven, Connecticut, the son of Amasa Goodyear, and the oldest of six children. His father was a descendant of Stephen Goodyear, succ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joseph Priestley
Joseph Priestley (; 24 March 1733 – 6 February 1804) was an English chemist, natural philosopher, separatist theologian, grammarian, multi-subject educator, and liberal political theorist. He published over 150 works, and conducted experiments in electricity and other areas of science. He was a close friend of, and worked in close association with Benjamin Franklin involving electricity experiments. Priestley is credited with his independent discovery of oxygen by the thermal decomposition of mercuric oxide, having isolated it in 1774. During his lifetime, Priestley's considerable scientific reputation rested on his invention of carbonated water, his writings on electricity, and his discovery of several "airs" (gases), the most famous being what Priestley dubbed "dephlogisticated air" (oxygen). Priestley's determination to defend phlogiston theory and to reject what would become the chemical revolution eventually left him isolated within the scientific community. Prie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Shilling
The shilling is a historical coin, and the name of a unit of modern currencies formerly used in the United Kingdom, Australia, New Zealand, other British Commonwealth countries and Ireland, where they were generally equivalent to 12 pence or one-twentieth of a pound before being phased out during the 20th century. Currently the shilling is used as a currency in five east African countries: Kenya, Tanzania, Uganda, Somalia, as well as the ''de facto'' country of Somaliland. The East African Community additionally plans to introduce an East African shilling. History The word ''shilling'' comes from Old English "Scilling", a monetary term meaning twentieth of a pound, from the Proto-Germanic root skiljaną meaning 'to separate, split, divide', from (s)kelH- meaning 'to cut, split.' The word "Scilling" is mentioned in the earliest recorded Germanic law codes, those of Æthelberht of Kent. There is evidence that it may alternatively be an early borrowing of Phoenician ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Edward Nairne
Edward Nairne (1726 – 1 September 1806) was English optician and scientific instrument maker. Biography Nairne was born in Sandwich, England. He was apprenticed to the optician Matthew Loft in 1741 and established his own business at 20 Cornhill in London after Loft's death in 1748. In 1774 he took his apprentice Thomas Blunt into partnership, a relationship that lasted until 1793 when Blunt opened his own shop at 22 Cornhill. Nairne patented several electrical machines, including an electrostatic generator consisting of a glass cylinder mounted on glass insulators; the device can supply either positive or negative electricity, and was intended for medicinal use. In the eighth edition of the instruction manual for this device he claimed that "electricity is almost a specific in some disorders, and deserves to be held in the highest estimation for its efficacy in many others". He recommended its use for nervous disorders, bruises, burns, scales, bloodshot eyes, toothache, sc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Meiji Period
The is an era of Japanese history that extended from October 23, 1868 to July 30, 1912. The Meiji era was the first half of the Empire of Japan, when the Japanese people moved from being an isolated feudal society at risk of colonization by Western powers to the new paradigm of a modern, industrialized nation state and emergent great power, influenced by Western scientific, technological, philosophical, political, legal, and aesthetic ideas. As a result of such wholesale adoption of radically different ideas, the changes to Japan were profound, and affected its social structure, internal politics, economy, military, and foreign relations. The period corresponded to the reign of Emperor Meiji. It was preceded by the KeiĹŤ era and was succeeded by the TaishĹŤ era, upon the accession of Emperor TaishĹŤ. The rapid modernization during the Meiji era was not without its opponents, as the rapid changes to society caused many disaffected traditionalists from the former samurai ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pumice
Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular volcanic rock that differs from pumice in having larger vesicles, thicker vesicle walls, and being dark colored and denser.Jackson, J.A., J. Mehl, and K. Neuendorf (2005) ''Glossary of Geology'' American Geological Institute, Alexandria, Virginia. 800 pp. McPhie, J., M. Doyle, and R. Allen (1993) ''Volcanic Textures A guide to the interpretation of textures in volcanic rocks'' Centre for Ore Deposit and Exploration Studies, University of Tasmania, Hobart, Tasmania..198 pp. Pumice is created when super-heated, highly pressurized rock is violently ejected from a volcano. The unusual foamy configuration of pumice happens because of simultaneous rapid cooling and rapid depressurization. The depressurization creates bubbles by lowering the solubi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sandstone
Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) because they are the most resistant minerals to weathering processes at the Earth's surface. Like uncemented sand, sandstone may be any color due to impurities within the minerals, but the most common colors are tan, brown, yellow, red, grey, pink, white, and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. Rock formations that are primarily composed of sandstone usually allow the percolation of water and other fluids and are porous enough to store large quantities, making them valuable aquifers and petroleum reservoirs. Quartz-bearing sandstone can be changed into quartzite through metamorphism, usually related to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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