 NASA scientist Homer E. Newell Jr. explaining principles of altitude, pressure, and temperature, c. 1973 | |
| Other names | Chalkboard, writing-board |
|---|---|
| Uses | Reusable writing surface on which text or drawings are made |
A blackboard or 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 Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.
A blackboard can simply be a board painted with a dark matte paint (usually black, occasionally dark green). [1] Matte black plastic sign material (known as closed-cell PVC foamboard) is also used to create custom chalkboard art. [2] Blackboards on an A-frame are used by restaurants and bars to advertise daily specials. [3] Adhesive chalkboard surface is also available in stores as rolls of textured black plastic shelf covering, which is applied to the desired wall, door or other surface.
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 porcelain-enameled steel (black, green, blue or sometimes other colours). Porcelain is very hard wearing, and blackboards made of porcelain usually last 10–20 years in intensive use. [4]
Lecture theatres may contain a number of blackboards in a grid arrangement. [5] The lecturer then moves boards into reach for writing and then moves them out of reach, allowing a large amount of material to be shown simultaneously.
The chalk marks can be easily wiped off with a damp cloth, a sponge or a special blackboard eraser usually consisting of a block of wood covered by a felt pad. However, chalk marks made on some types of wet blackboard can be difficult to remove. Blackboard manufacturers often advise that a new or newly resurfaced blackboard be completely covered using the side of a stick of chalk and then that chalk brushed off as normal to prepare it for use.[ citation needed ]
Chalk sticks are produced in white and in various colours, especially for use with blackboards. White chalk sticks are made mainly from calcium carbonate derived from mineral chalk or limestone, while coloured chalk sticks are made from calcium sulphate in its dihydrate form, CaSO4·2H2O, derived from gypsum. [6] [7] Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO3 (calcite).
 | This section possibly contains original research .(October 2023) |
On the other hand, chalk produces dust, the amount depending on the quality of chalk used. Some people find this uncomfortable or may be allergic to it, and according to the American Academy of Allergy, Asthma and Immunology (AAAAI), there are links between chalk dust and allergy and asthma problems. [8] The dust also precludes the use of chalk in areas shared with dust-sensitive equipment such as computers. The writing on blackboards is difficult to read in the dark. Chalk sticks shrink through use, and are notorious for breaking in half unless inserted in a writing utensil designed for chalk. Blackboards can suffer from ghosting. Ghosting occurs when old coloured chalk, pastels or chalkpen ink absorbs into the black finish of the board, making it impossible to remove. [9]
The scratching of fingernails on a blackboard, as well as other pointed, especially metal objects against blackboards, produces a sound that is well known for being extremely irritating to most people. [10] According to a study run by Michael Oehler, a professor at the University of Cologne, Germany, humans are "predisposed to detest" the sound of nails on a blackboard. [11] The findings of the study were presented at the Acoustical Society of America conference and support earlier findings from a 1986 study by Vanderbilt psychologist Randolph Blake and two colleagues found that the sound of nails on a chalkboard annoyed people even when the high-pitch frequencies were removed. The study earned Blake a 2006 Ig Nobel Prize. [12]
The writing slate was in use in Indian schools as mentioned in Alberuni's Indica (Tarikh Al-Hind), written in the early 11th century:
They use black tablets for the children in the schools, and write upon them along the long side, not the broadside, writing with a white material from the left to the right. [13]
The first classroom uses of large blackboards are difficult to date, but they were used for music education and composition in Europe as far back as the 16th century. [14] The term "blackboard" is attested in English from the mid-18th century; the Oxford English Dictionary provides a citation from 1739, to write "with Chalk on a black-Board". [15] The first attested use of chalk on blackboard in the United States dates to September 21, 1801, in a lecture course in mathematics given by George Baron. [16] James Pillans has been credited with the invention of coloured chalk (1814); he had a recipe with ground chalk, dyes and porridge. [17]
The use of blackboards changed methods of education and testing, as found in the Conic Sections Rebellion of 1830 in Yale. [18] Manufacturing of slate blackboards began by the 1840s. [4] Green porcelain enamel surface, was first used in 1930, and as this type of boards became popular, the word "chalkboard" appeared. [4] In the US green porcelain enamelled boards started to appear at schools in 1950s. [19]
The dictionary definition of blackboard at Wiktionary The dictionary definition of chalkboard at Wiktionary
Media related to Blackboards at Wikimedia Commons| National | |
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Slate is a fine-grained, foliated, homogeneous, metamorphic rock derived from an original shale-type sedimentary rock composed of clay or volcanic ash through low-grade, regional metamorphism. It is the finest-grained foliated metamorphic rock. Foliation may not correspond to the original sedimentary layering, but instead is in planes perpendicular to the direction of metamorphic compression.
Calcium carbonate is a chemical compound with the chemical formula CaCO3. It is a common substance found in rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skeletons and pearls. Materials containing much calcium carbonate or resembling it are described as calcareous. Calcium carbonate is the active ingredient in agricultural lime and is produced when calcium ions in hard water react with carbonate ions to form limescale. It has medical use as a calcium supplement or as an antacid, but excessive consumption can be hazardous and cause hypercalcemia and digestive issues.
Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Chalk is common throughout Western Europe, where deposits underlie parts of France, and steep cliffs are often seen where they meet the sea in places such as the Dover cliffs on the Kent coast of the English Channel.
A bulletin board is a surface intended for the posting of public messages, for example, to advertise items wanted or for sale, announce events, or provide information. Bulletin boards are often made of a material such as cork to facilitate addition and removal of messages, as well as a writing surface such as blackboard or whiteboard. A bulletin board which combines a pinboard (corkboard) and writing surface is known as a combination bulletin board. Bulletin boards can also be entirely in the digital domain and placed on computer networks so people can leave and erase messages for other people to read and see, as in a bulletin board system.
Vitreous enamel, also called porcelain enamel, is a material made by fusing powdered glass to a substrate by firing, usually between 750 and 850 °C. The powder melts, flows, and then hardens to a smooth, durable vitreous coating. The word vitreous comes from the Latin vitreus, meaning "glassy".
A whiteboard is a glossy, usually white surface for making non-permanent markings. Whiteboards are analogous to blackboards, but with a smoother surface allowing for rapid marking and erasing of markings on their surface. The popularity of whiteboards increased rapidly in the mid-1990s and they have become a fixture in many offices, meeting rooms, school classrooms, public events and other work environments.
A marker pen, fine liner, marking pen, felt-tip pen, felt pen, flowmarker, sign pen, vivid, flomaster, texta, sketch pen, koki or simply marker is a pen which has its own ink source and a tip made of porous, pressed fibers such as felt. A marker pen consists of a container and a core of an absorbent material that holds the ink. The upper part of the marker contains the nib that was made in earlier times of a hard felt material, and a cap to prevent the marker from drying out.
A permanent marker or indelible marker is a type of marker pen that is used to create permanent or semi-permanent writing on an object.
An eraser is an article of stationery that is used for removing marks from paper or skin. Erasers have a rubbery consistency and come in a variety of shapes, sizes, and colors. Some pencils have an eraser on one end. Erasers can come in various shapes and colors. 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.
A slate is a thin piece of hard flat material, historically slate stone, which is used as a medium for writing.
Chalk is a type of sedimentary rock, composed predominantly of calcium carbonate.
An interactive whiteboard (IWB), also known as interactive board, interactive display, interactive digital board or smart board, is a large interactive display board in the form factor of a whiteboard. It can either be a standalone touchscreen computer used independently to perform tasks and operations, or a connectable apparatus used as a touchpad to control computers from a projector. They are touch screen enabled small computers.They are used in a variety of settings, including classrooms at all levels of education, in corporate board rooms and work groups, in training rooms for professional sports coaching, in broadcasting studios, and others.
Go equipment refers to the board, stones, and bowls for the stones required to play the game of Go. The quality and materials used in making Go equipment varies considerably, and the cost varies accordingly from economical to extremely expensive.
Coated paper is paper that has been coated by a mixture of materials or a polymer to impart certain qualities to the paper, including weight, surface gloss, smoothness, or reduced ink absorbency. Various materials, including kaolinite, calcium carbonate, bentonite, and talc, can be used to coat paper for high-quality printing used in the packaging industry and in magazines.
Ceramic glaze, or simply glaze, is a glassy coating on ceramics. It is used for decoration, to ensure the item is impermeable to liquids and to minimise the adherence of pollutants.
Wet-wipe markers or wet-erase markers are a type of writing implement, which are used primarily on overhead transparencies, tablets at restaurants, and office calendars. Other uses include writing on mirrors, chalkboards, plastics, ceramics, glass windows and other non-porous surfaces. The contents of these markers are water, resin, and titanium dioxide.
A chalkboard eraser is a special type of eraser specifically used to erase chalk markings on slating paint. It is most commonly made of felt strips attached to a handle. Chalkboard erasers are typically broad and rectangular, intended to clear large areas for new content as part of a lecture or presentation.
A Lénárt sphere is an educational manipulative and writing surface for exploring spherical geometry, invented by Hungarian István Lénárt as a modern replacement for a spherical blackboard. It can be used for visualizing the geometry of points, great and small circles, triangles, polygons, conics, and other objects on a sphere, and comparing spherical geometry to Euclidean geometry as drawn on a flat piece of paper or blackboard. The included spherical ruler and compass support synthetic straightedge and compass construction on the sphere.
Sidewalk chalk is typically large and thick sticks of chalk that come in multiple colors and are mostly used for drawing on pavement or concrete sidewalks, frequently four square courts or a hopscotch boards. Blackboard chalk, typically used in educational settings, is shorter and thinner than sidewalk chalk.
Do Not Erase: Mathematicians and their Chalkboards is a photo-essay book on the blackboards of mathematicians. It was photographed and edited by Jessica Wynne, and published in 2021 by the Princeton University Press.
