A chalkboard or blackboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulfate or calcium carbonate, known, when used for this purpose, as chalk. Chalkboards were originally made of smooth, thin sheets of black or dark grey slate stone. Modern versions are often green because this is considered easier on the eyes.
A chalkboard can simply be a piece of board painted with matte dark paint (usually black or dark green). 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 chalkboards are made of a rougher version porcelain enamelled steel (black, green, blue or sometimes other colours). Porcelain is very hard wearing and chalkboards made of porcelain usually last 10–20 years in intensive use.
The chalk marks can be easily wiped off with a damp cloth, a sponge or a special chalkboard eraser consisting of a block of wood covered by a felt pad. However, chalk marks made on some types of wet chalkboard can be difficult to remove. Chalkboard manufacturers often advise that a new or newly resurfaced chalkboard be completely covered using the side of a stick of chalk and then that chalk brushed off as normal to prepare it for use.
Sticks of processed "chalk" are produced especially for use with chalkboards in white and also in various colours. These are not actually made from chalk rock but from calcium sulfate in its dihydrate form, gypsum.
Chalkboards are often used in teaching, although in wealthier countries their use has diminished. University lecture theatres may contain a number of chalkboards in a grid arrangement, with each column mounted on rollers to allow the lecturer to move boards into reach for writing and then move them out of reach, allowing a large amount of material to be shown simultaneously. Chalkboards are also used in many establishments (typically public houses) as a form of advertising often for upcoming events and menus and to record the score in darts matches. Also in homes, specifically in the kitchen, for writing messages, shopping lists and things to remember, as well as sometimes serving a decorative purpose.
Advantages and disadvantages
As compared to whiteboards, chalkboards have a variety of advantages:
- Chalk requires no special care; whiteboard markers must be capped or else they dry out.
- Chalk is an order of magnitude cheaper than whiteboard markers for a comparable amount of writing.
- It is easier to draw lines of different weights and thicknesses with chalk than with whiteboard markers.
- Chalk has a mild smell, whereas whiteboard markers often have a pungent odor.
- Chalk writing often provides better contrast than whiteboard markers, which helps people read at a distance.
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. The dust also precludes the use of chalk in areas shared with dust-sensitive equipment such as computers.
The scratching of fingernails on a chalkboard, as well as other pointed, especially metal objects against chalkboards, produces a sound that is well-known for being extremely irritating to most people. Many are averse also to merely the sight or thought of this sort of contact.
Etymology and history
Portable chalkboard in a mind-reading performance, 1900
- Chalkboard gag from The Simpsons
- Interactive whiteboard
- Sidewalk chalk
- Sound of fingernails scraping chalkboard
- ^ "Why Is the Blackboard Green?". Your Dictionary. http://answers.yourdictionary.com/technology/inventions/why-is-the-blackboard-green.html. Retrieved 1 October 2011.
- ^ WebMD. "Reading, Writing, and Wheezing? Not Necessarily". Asthma Health Center. WebMD. http://www.webmd.com/asthma/news/20000919/reading-writing-wheezing-not-necessarily. Retrieved Sept. 19, 2000.
- ^ "Blackboard – Dictionary.com". http://dictionary.reference.com/browse/blackboard.
- ^ "Chalkboard – Dictionary.com". http://dictionary.reference.com/browse/chalkboard.
- ^ "The Cato Education Market Index". http://cato.org/pubs/pas/pa585.pdf
- ^ About Blackboards - Blackboard Technology and Chalkboard History Advances
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Look at other dictionaries:
chalkboard — chalk board (ch[add]k b[=o]rd ), n. a dark sheet of slate used as a surface for writing on, with chalk. Syn: blackboard. [WordNet 1.5] … The Collaborative International Dictionary of English
chalkboard — (n.) also chalk board, 1816, from CHALK (Cf. chalk) (n.) + BOARD (Cf. board) (n.1) … Etymology dictionary
chalkboard — ☆ chalkboard [chôk′bôrd΄ ] n. BLACKBOARD … English World dictionary
chalkboard — UK [ˈtʃɔːkˌbɔː(r)d] / US [ˈtʃɔkˌbɔrd] noun [countable] Word forms chalkboard : singular chalkboard plural chalkboards mainly American a blackboard … English dictionary
chalkboard — chalk|board [ˈtʃo:kbo:d US ˈtʃo:kbo:rd] n AmE a ↑blackboard ▪ She wrote the day s menu up on a chalkboard … Dictionary of contemporary English
chalkboard — [[t]tʃɔ͟ːkbɔː(r)d[/t]] chalkboards N COUNT A chalkboard is a dark coloured board that you can write on with chalk. Chalkboards are often used by teachers in the classroom. [mainly AM] (in BRIT, use blackboard) … English dictionary
chalkboard — noun (C) AmE a blackboard: Thanks, but the janitor cleans the chalkboard … Longman dictionary of contemporary English
chalkboard — noun Date: 1936 blackboard … New Collegiate Dictionary
chalkboard — /chawk bawrd , bohrd /, n. a blackboard, esp. a green or other light colored one. [1935 40, Amer.; CHALK + BOARD] * * * … Universalium
chalkboard — noun (esp. AmE) ⇨ See ↑blackboard … Collocations dictionary