Chalk
Probably no one misses the task of clapping together elementary school erasers to clean them, but chalk is still essential to many sports and art endeavors.
Credit: iStock
Before performing a routine on the uneven parallel bars, gymnasts coat the palms of their hands with a white powder and clap their hands, raising a cloud of dust. The white powder is chalk, which reduces friction so gymnast’s hands will move smoothly over the bar. Chalk is hygroscopic, meaning it absorbs water, so it counteracts sweaty palms that might otherwise cause a gymnast to slip. Similarly, rock climbers and weight lifters use chalk to ensure a reliable grip.
Chalk is a sedimentary rock that is a form of limestone, calcium carbonate, and is formed deep underwater by the gradual deposition of dead microorganisms. Because chalk is highly resistant to weathering, it is often revealed along coastlines such as the famed white cliffs of Dover in England. Chalk’s ability to absorb water is related to its high porosity; underground chalk retains ground water, releasing it slowly to create a valuable reservoir of water during dry seasons.
Used since prehistoric times, chalk’s tendency to powder and leave a residue made it one of the earliest media used by artists for drawing. In the 16th century during the Renaissance, Italian artists began the tradition of using pavement as their canvases. Chalk drawings have evolved into a type of performance art in which conversations with and observation by spectators is as important to the process as is the creation of the finished work. Many of us also associate memories of school classrooms with blackboards and chalk dust created by clapping erasers together.
More information about the history of chalk art may be found at http://www.visual-arts-cork.com/drawing/chalk-drawings.htm. Kurt Wenner is one of many exceptional, contemporary street artists: http://kurtwenner.com/street.htm
This topic was recommended by Susan Samuels of Granby, CT