Blackboard (or chalkboard) is an important instructional material and ubiquitous in almost all learning institutions from the 19th century up to this century. The first chalkboards are made of black slates, partner with white chalk for writing. The tandem turned out to be favorable to most because of their contrasting colors, it is very easy to see writings made by white chalk on the black-colored chalkboard. Like other technologies, chalkboard also evolved from being made of black slate to the versions made of plywood painted with black paint or coated with coarse black porcelain. And like its partner, as the time goes by (chalk has a variety of color), chalkboard has also become available in a variety of colors like brown and the more famous green. The shift of chalkboard color from black to green has some good reasons: chalk writings on the blackboard when erased leaves white "ghost writings" because chalk particles are deposited on pores of the blackboard, and these writings are easily noticeable. Our eyes also get stressed if we stare on black-colored objects for a long duration and can increase the chance of blindness. Green-colored chalkboard, on the other hand, gives relaxing, soothing effect to our eyes. Green-colored chalkboard should be called greenboard, and not blackboard. But the term "blackboard" has become so popular that it has become embedded into the vocabulary of older generations, referring greenboards to the younger generations as blackboards. In turn, younger generations also refer greenboards as blackboards.
Next BIG question: Can poison kill if it is already EXPIRED?
Next BIG question: Can poison kill if it is already EXPIRED?