blackboard

{{Infobox laboratory equipment

| name = Blackboard

| image = Homer E Newell NASA.jpg

| caption = NASA scientist Homer E. Newell Jr. explaining principles of altitude, pressure, and temperature, {{circa|1973}}

| acronym =

| other_names = Chalkboard, writing-board

| uses = Reusable writing surface on which text or drawings are made

| material =

| components =

| related =

}}

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, better known as chalk.

Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.

Design

File:Chalkboard eraser, Waldorf School, East Lexington MA.jpg

A blackboard can simply be a board painted with a dark matte paint (usually black, occasionally dark green).{{cite web|url=https://indianexpress.com/article/india/india-others/cpm-slams-use-of-green-boards-in-kerala-schools/|title=CPM slams use of green boards in Kerala schools|last=Philip|first=Shaju|newspaper=The Indian Express|date=June 30, 2014|access-date=February 17, 2021}} Matte black plastic sign material (known as closed-cell PVC foamboard) is also used to create custom chalkboard art.{{cite web|url=http://www.kansas.com/living/home-garden/article1093159.html|title=The ABCs of chalkboard paint|last=Downs|first=Stacy|newspaper=The Wichita Eagle|date=June 1, 2012|access-date=February 17, 2021}} Blackboards on an A-frame are used by restaurants and bars to advertise daily specials.{{cite web|url=https://www.squaresigns.com/blog/temporary-signage-ideas-for-restaurants|title=Temporary Signage Ideas For Restaurants|last=Goldsworthy|first=Jessica|website=squaresigns.com|date=September 23, 2018|access-date=February 17, 2021}} 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.

Lecture theatres may contain a number of blackboards in a grid arrangement.{{Cite web|date=2013-06-27|title=Film Locations: The Most Filmed College Classroom Is Inside Columbia University's Havemeyer Hall|url=https://untappedcities.com/2013/06/27/film-locations-the-most-filmed-college-classroom-is-inside-columbia-universitys-havemeyer-hall/|access-date=2021-03-21|website=Untapped New York|language=en-US}} 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.

Chalk sticks

File:Craie2.jpg

File:Chalkboard-writing.ogg

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.{{cite web|url=http://www.madehow.com/Volume-1/Chalk.html|title=How chalk is made – material, making, used, processing, procedure, product, industry |website=madehow.com|access-date=February 17, 2021}}{{cite journal|title=Allergic contact dermatitis caused by metals in blackboard chalk: a case report|journal=Acta Dermato-Venereologica |author=Corazza, M. |author2=Zauli, S. |author3=Pagnoni, A. |author4=Virgili, A.|volume=92|issue=4|year=2012|pages=436–437|doi=10.2340/00015555-1296|pmid=22367154|doi-access=free}} Chalk sticks containing calcium carbonate typically contain 40–60% of CaCO₃ (calcite).

Issues with use

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.{{cite web|title=Reading, Writing, and Wheezing? Not Necessarily|url=http://www.webmd.com/asthma/news/20000919/reading-writing-wheezing-not-necessarily|publisher=WebMD|date=September 19, 2000|access-date=February 13, 2021}} 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.{{Cite web|title=What Are Chalkboards {{!}} Majisign|url=https://www.majisign.co.uk/article/what-are-chalkboards#Blackboardghosting|access-date=2021-03-21|website=www.majisign.co.uk|date=21 November 2020 }}

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.{{cite journal|last=Wong|first=Sam|title=The feeling you get when nails scratch a blackboard has a name|journal=New Scientist |issue=3115|date=February 28, 2017|url=https://www.newscientist.com/article/2123018-the-feeling-you-get-when-nails-scratch-a-blackboard-has-a-name/|access-date=February 17, 2021}} 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.{{cite web| url=https://www.npr.org/2011/11/09/142184389/why-nails-on-a-chalkboard-drives-us-crazy | title=Why Nails On A Chalkboard Drives Us Crazy |last=Siegel|first=Robert|date=November 9, 2011|publisher=NPR | access-date=February 17, 2021}} 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.{{cite magazine| url=https://content.time.com/time/specials/packages/article/0,28804,1996489_1996488_1996483,00.html | title=Top 10 Most Annoying Sounds: Nails on a Chalkboard | author=Frances Romero |date=14 June 2010 | magazine=Time |access-date=31 May 2016}}

Etymology and history

File:Teacher at blackboard (1924).jpg

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.{{cite book| url=https://archive.org/stream/alberunisindiaac01biru#page/182/mode/2up| title=Alberuni's India. An account of the religion, philosophy, literature, geography, chronology, astronomy, customs, laws and astrology of India about A.D. 1030| year=1910}}

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.{{cite book|url=https://books.google.com/books?id=MXc8DwAAQBAJ&pg=PA82|title=Composers at Work: The Craft of Musical Composition, 1450-1600|page=82|last=Owens|first=Jessie Ann|publisher=Oxford University Press|year=1998|isbn=978-0-19-512904-5|via=Google Books}} 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".Entry for [http://www.oed.com/view/Entry/19691 "blackboard, n{{-"}}], in the Oxford English Dictionary (Third ed., 2011) 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.{{cite book|author=Stephen E. Ambrose|title=Duty, Honour, Country: A History of West Point|url=https://books.google.com/books?id=SC5wr5A_hbkC&pg=PA19|access-date=14 February 2013|date=1 December 1999|publisher=JHU Press|isbn=978-0-8018-6293-9|page=19}} James Pillans has been credited with the invention of coloured chalk (1814); he had a recipe with ground chalk, dyes and porridge.{{cite book|author=Jo Swinnerton|title=The History of Britain Companion|url=https://books.google.com/books?id=hd0wNKXAupwC&pg=PA128|access-date=14 February 2013|date=30 September 2005|publisher=Anova Books|isbn=978-1-86105-914-7|page=128}}

The use of blackboards changed methods of education and testing, as found in the Conic Sections Rebellion of 1830 in Yale.{{cite journal|url=https://www.ams.org/notices/200209/comm-smithsonian.pdf|title=Teaching Math in America: An Exhibit at the Smithsonian|last=Jackson|first=Allyn|journal=Notices of the American Mathematical Society|page=1082|volume=49|issue=9|year=2002|access-date=February 17, 2021}}

Manufacturing of slate blackboards began by the 1840s.{{cite book|url=https://books.google.com/books?id=sl5GAwAAQBAJ&pg=PT45|page=45|title=Blackboard: A Personal History of the Classroom|last=Buzbee|first=Lewis|publisher=Graywolf Press|year=2014|isbn=978-1-55597-683-5|via=Google Books}} Green porcelain enamel surface was first used in 1930, and as this type of boards became popular, the word "chalkboard" appeared. In the US green porcelain enamelled boards started to appear at schools in 1950s.{{cite journal|url=https://books.google.com/books?id=oiEDAAAAMBAJ&pg=PA144|page=144|title=I Found My Future in the Past|last=David|first=Lester|journal=Popular Science|date=April 1952|issue=April 1952|issn=0161-7370|via=Google Books}}

Gallery

File:Kyomachi No.8 Café welcome blackboard 20190406.jpg|An advertising blackboard in Taipei, Taiwan, 2019

File:The board.jpg|Mathematics on a board, 2017

File:ASC Leiden - Coutinho Collection - 12 18 - Campada college on the northern frontline, Guinea-Bissau - 1973.tif|Teacher explaining the decimal system of weights using a blackboard, Guinea-Bissau, 1974

File:Lembeck mit 5-HT.jpg|An Austrian chemist with colored chalk, 1970

File:Boy in school, 1961 (52338002867).jpg|A schoolboy in Seattle, WA, USA, 1961