What Are the Line Markings on Fields Made Of?

The markings on athletic fields are made from powdered limestone, which is calcium carbonate (CaCO3) a safe, widely used mineral compound that is found naturally or can be produced synthetically. This white powdery substance shouldn't be confused with calcium oxide, also known as lime or quicklime.

  1. Origin

    • A yard line marking on a football field.

      Made by pulverizing limestone and marble, this form of calcium carbonate, obtained from natural sources, is used in ceramics, printing, paint, agriculture, food and medical products. Common chalk is formed from the remains of microscopic marine organisms. It is a non-toxic white powder as opposed to hydrated lime, which is alkaline and highly toxic.

    Historic Sports Use

    • In the 1950s, the early days of professional football, team officials tried many different things to mark the lines. Dry lime, marble dust and the white dust produced by burnt anthracite coal were all used. So was hydrated lime, which burned the eyes. Some teams even tried mixing flakes of laundry detergent with bluing agents. Eventually they were all abandoned in favor of calcium carbonate, now called field marking chalk or dust. With the advent of turf fields, paint products took the place of powders.

    Applications

    • Chalk or dust is marketed by sports supply companies and sold in 50-lb. bags to line a baseball or softball diamond. To produce straight, even lines, professionals use a machine called a Dry Line Marker -- a bucket on a wheel with an exit spout. Some marking systems are useful on fields that have not been previously marked.

    Warnings

    • Although considered completely safe and approved by the NCAA (National Collegiate Athletic Association) for use on football, soccer, softball and baseball fields, calcium carbonate should be labeled as Field Marking Dust or Chalk to keep from using the toxic forms. Some reported injuries reported are tied to using quicklime products by mistake.