page_title: Blackboard
section_title: Design
hierarchical_section_title: Blackboard / Design
caption_attribution_description: English: Blank chalkboard and duster.
context_page_description: A 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. Blackboards were originally made of smooth, thin sheets of black or dark grey slate stone.
context_section_description: A blackboard can simply be a board painted with matte dark paint (usually black, occasionally dark green).  Matte black plastic sign material (known as ‘closed-cell PVC foamboard’) is also used to create custom chalkboard art.
  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 a rougher version porcelain enamelled 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.
  Manufacturing of slate blackboards began by the 1840s. Green chalkboards, generally made of porcelain enamel on a steel base, first appeared in the 1960s.
  Lecture theatres may contain a number of blackboards in a grid arrangement. 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.
caption: A modern chalkboard, 2014.
exif: {"Image Make": "NIKON CORPORATION", "Image Model": "NIKON D5100", "Image Orientation": "Horizontal (normal)", "Image XResolution": "300", "Image YResolution": "300", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Ver.1.01", "Image DateTime": "2014:10:29 20:58:04", "Image YCbCrPositioning": "Co-sited", "Image ExifOffset": "228", "GPS GPSVersionID": "[2, 3, 0, 0]", "Image GPSInfo": "33760", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "300", "Thumbnail YResolution": "300", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "33888", "Thumbnail JPEGInterchangeFormatLength": "12375", "Thumbnail YCbCrPositioning": "Co-sited", "EXIF ExposureTime": "1/15", "EXIF FNumber": "71/10", "EXIF ExposureProgram": "Aperture Priority", "EXIF ISOSpeedRatings": "640", "EXIF SensitivityType": "Recommended Exposure Index", "EXIF ExifVersion": "0230", "EXIF DateTimeOriginal": "2014:10:29 20:58:04", "EXIF DateTimeDigitized": "2014:10:29 20:58:04", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "4", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "19/5", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire", "EXIF FocalLength": "20", "EXIF SubSecTime": "00", "EXIF SubSecTimeOriginal": "00", "EXIF SubSecTimeDigitized": "00", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "4928", "EXIF ExifImageLength": "3264", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "33730", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CVAPattern": "[0, 2, 0, 2, 0, 1, 1, 2]", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "1", "EXIF FocalLengthIn35mmFilm": "30", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "Low gain up", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}