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Ink Eraser
An ink eraser is an instrument used to scrape away or chemically bleach ink from a writing surface. This is a more involved process than removing pencil markings. Pencil marks can be gradually adhered to natural rubber fragments by rubbing the mark with a pencil eraser (this action is what prompted Joseph Priestly to give solidified latex its common name.) Ink, however readily penetrates the fibers of most papers and is therefore more difficult to extract by mechanical action. Older ink erasers are therefore small knives designed to scrape off the top few microns of a sheet of paper, removing the ink that had penetrated. In concert with bladed ink erasers an eraser similar to those at the end of pencils was also used, with additional abrasives, such as sand, mixed into the rubber. Fibreglass ink erasers also work by abrasion. These erasers physically remove the ink and the paper it has marked from the larger sheet. The chemical ink eradicator contains a substance that reacts wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pelikan
Pelikan Holding AG is a German manufacturing company of writing, office and art equipment. Credited with the invention of the differential-piston filling method, the original company was founded in Hanover in 1838 before it went bankrupt and restarted. Through a reverse takeover on 8 April 2005, Pelikan Holding AG is now an Aktiengesellschaft company (limited by shared ownership), part of the Pelikan Group GmbH. Nowadays, Pelikan manufacture a wide range of products including writing implements, art materials and office goods. History The roots of the company can be traced back to 1838, when chemist Carl Hornemann founded a color and ink factory in Hanover, Germany. The date of the first price list of the company – 28 April – is set up as the company's foundation date. In 1863, Guenther Wagner obtained the position of chemist and plant manager. He took over the company in 1871. Wagner algo designed the company first logo (taking the figure of a pelican from his ow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Writing Implements
A writing implement or writing instrument is an object used to produce writing. Writing consists of different figures, lines, and or forms. Most of these items can be also used for other functions such as painting, drawing and technical drawing, but writing instruments generally have the ordinary requirement to create a smooth, controllable line. Another writing implement employed by a smaller population is the stylus used in conjunction with the slate for punching out the dots in Braille. Autonomous An autonomous writing implement is one that cannot "run out"—the only way to render it useless is to destroy it. Without pigment The oldest known examples were created by incising a flat surface with a rigid tool rather than applying pigment with a secondary object, e.g., Chinese jiaguwen carved into turtle shells. However, this may simply represent the relative durability of such artifacts rather than truly representing the evolution of techniques, as the meaningful application o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eraser
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 in ink. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Deinking
Deinking is the industrial process of removing printing ink from paperfibers of recycled paper to make deinked pulp. The key in the deinking process is the ability to detach ink from the fibers. This is achieved by a combination of mechanical action and chemical means. In Europe the most common process is froth flotation deinking. Paper is one of the main targets for recycling. A concern about recycling wood pulp paper is that the fibers are degraded with each cycle and after being recycled 4–6 times the fibers become too short and weak to be useful in making paper. History Before the invention of the paper machine in 1799 the most common fibre source was recycled fibres from used textiles, hence the name rag paper. The rags were from hemp, linen and cotton. It was not until the introduction of wood pulp in 1843 that paper production was independent of recycled materials. Recycling of used paper before the industrialisation of paper production, rag paper was recycl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aldehyde
In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group. Aldehydes are common and play important roles in the technology and biological spheres. Structure and bonding Aldehydes feature a carbon center that is connected by a double bond to oxygen and a single bond to hydrogen and single bond to a third substituent, which is carbon or, in the case of formaldehyde, hydrogen. The central carbon is often described as being sp2- hybridized. The aldehyde group is somewhat polar. The C=O bond length is about 120-122 picometers. Physical properties and characterization Aldehydes have properties that are diverse and that depend on the remainder of the molecule. Smaller aldehydes are more soluble in water, formaldehyde and acetaldehyde completely so. The volatile aldehydes have pungent odors. Al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three isotopes occur naturally, C and C being stable, while C is a radionuclide, decaying with a half-life of about 5,730 years. Carbon is one of the few elements known since antiquity. Carbon is the 15th most abundant element in the Earth's crust, and the fourth most abundant element in the universe by mass after hydrogen, helium, and oxygen. Carbon's abundance, its unique diversity of organic compounds, and its unusual ability to form polymers at the temperatures commonly encountered on Earth, enables this element to serve as a common element of all known life. It is the second most abundant element in the human body by mass (about 18.5%) after oxygen. The atoms of carbo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and hydrogen atom held together by a single covalent bond, and carries a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, a ligand, a nucleophile, and a catalyst. The hydroxide ion forms salts, some of which dissociate in aqueous solution, liberating solvated hydroxide ions. Sodium hydroxide is a multi-million-ton per annum commodity chemical. The corresponding electrically neutral compound HO• is the hydroxyl radical. The corresponding covalently bound group –OH of atoms is the hydroxy group. Both the hydroxide ion and hydroxy group are nucleophiles and can act as catalysts in organic chemistry. Many inorganic substances which bear the word ''hydroxide'' in their names are not ionic compounds of the hydroxide ion, but covalent compounds which contain hydroxy groups. Hydroxide ion The hydroxide ion is a natural p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfite
Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are widely used. Sulfites are substances that naturally occur in some foods and the human body. They are also used as regulated food additives. When in food or drink, sulfites are often lumped together with sulfur dioxide.SeREGULATION (EU) No 1169/2011 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL/ref> Structure The structure of the sulfite anion can be described with three equivalent resonance structures. In each resonance structure, the sulfur atom is double-bonded to one oxygen atom with a formal charge of zero (neutral), and sulfur is singly bonded to the other two oxygen atoms, which each carry a formal charge of −1, together accounting for the −2 charge on the anion. There is also a non-bonded lone pair on the sulfur, so the st ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pointe Effaceur
Pointe technique ( ) is the part of classical ballet technique that concerns ''pointe work'', in which a ballet dancer supports all body weight on the tips of fully extended feet within pointe shoes. A dancer is said to be ''en pointe'' () when the dancer's body is supported in this manner, and a fully extended vertical foot is said to be ''en pointe'' when touching the floor, even when not bearing weight. Pointe technique resulted from a desire for female dancers to appear weightless and sylph-like. Although both men and women are capable of pointe work, it is most often performed by women. Extensive training and practice are required to develop the strength and technique needed for pointe work. Typically, dance teachers consider factors such as age, experience, strength and alignment when deciding whether to allow a dancer to begin pointe work. Technique Pointe technique encompasses both the mechanical and artistic aspects of pointe work. In particular, it is concerned wi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Joseph Priestly
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] |
List Of Unusual Deaths
This list of unusual deaths includes unique or extremely rare circumstances of death recorded throughout history, noted as being unusual by multiple sources. Antiquity Middle Ages Renaissance Early modern period 19th century 20th century 1901–1960 1960s 1970s 1980s 1990s 21st century 2000s 2010s 2020s Animal deaths This section is for the deaths of animals, for whom there are several sources mentioning the deaths as unusual. See also * Autoerotic fatality * Darwin Awards * Death by coconut * Death from laughter * Execution by elephant * Spontaneous human combustion * ''1000 Ways to Die'' * Death during consensual sex Lists * List of association footballers who died while playing * List of causes of death by rate * List of racing cyclists and pacemakers with a cycling-related death * List of entertainers who died during a performance * List of inventors killed by their own invention * List of last words * List ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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