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A blackboard, also known as a chalkboard, is a writing surface that allows text or drawings to be made using sticks of calcium sulfate or calcium carbonate, commonly referred to as chalk. Traditionally, blackboards were crafted from smooth, thin sheets of black or dark gray slate stone. However, modern blackboards can be made from various materials, including matte-painted boards, matte black plastic sign material, or even coiled sheets of plastic drawn across parallel rollers for additional writing space.
Restaurants and bars often use blackboards mounted on A-frames to advertise daily specials, while a more contemporary variation involves using porcelain enameled steel for increased durability. This type of blackboard can last up to 10-20 years in intensive use. Lecture theaters may feature multiple blackboards arranged in a grid layout, allowing presenters to easily access and display large amounts of material simultaneously.
To erase chalk marks, a damp cloth, sponge, or special blackboard eraser is typically used. However, chalk marks made on certain types of wet blackboards may prove challenging to remove. Manufacturers often recommend covering a new or newly resurfaced blackboard entirely with chalk and then brushing it off to prepare it for use.
While the exact origins of large blackboards in classrooms are difficult to pinpoint, they have been used for music education and composition in Europe since at least the 16th century. The term "blackboard" dates back to the mid-18th century, with the first documented use of chalk on a blackboard in the United States occurring in 1801 during a mathematics lecture given by George Baron. James Pillans is credited with inventing colored chalk in 1814, which significantly influenced educational methods and testing. Manufacturing of slate blackboards began in the 1840s, and the introduction of green porcelain enamel surfaces in the 1930s led to the popularization of the term "chalkboard." Green porcelain enamel boards became prevalent in American schools during the 1950s.
