Climbers use chalk on their hands to dry sweat and moisture on their hands and fingers, attempting to improve their grip on handholds. Chalk or powdered magnesium carbonate is usually carried in a sack called a chalk bag which is attached to a belt around the climber’s waist or clipped onto a gear loop on a harness. Climbers have used chalk since it was first introduced into climbing by John Gill, the father of bouldering and a former gymnast, in the 1950s.
Chalk Keeps Hands from Slipping. Climbers using chalk as a drying agent, dip their fingers and hands into chalk bags, covering the skin with the chalk and then either shaking or blowing off the excess chalk. The chalk on their hands then allows the climber to feel secure on handholds. If you climb on hot days, you quickly learn that chalk can keep your hands from slipping off holds.
Climbing Chalk is Crushed Limestone Climbing chalk, usually white in color, is made from limestone and dolomite, which are mined and then processed into various products including magnesium carbonate or chalk. Chalk is purified, dried, and then cut into blocks or crushed into a fine powder. Some manufacturers that make climbing-specific chalk like Metolius Climbing also add ingredients for more moisture absorption before packaging and selling climbing chalk. The chalk is sold for athletic use for not only climbers but also for gymnasts and weightlifters.
There is no research that confirms that chalk actually enhances a climber’s performance and some evidence indicates that climbing chalk may decrease the friction of skin on rock. A 2001 study at the University of Birmingham in the United Kingdom found that “chalk decreased the coefficient of friction,” which is “the ratio between the tangential force (pulling the rock) and the normal force (applied by the participants).” The study found that chalk dries the skin, decreasing its ability to grip the rock surface with friction, and that chalk creates a “slippery granular layer.” It concludes that climbers should find other means of drying sweat and moisture on their hands to increase friction.
Most climbers, however, feel that the evil white dust does indeed help dry their hands and fingers and allow them to grip the rock surface more effectively. Use chalk sparingly when you dip your hand in your chalk bag; too much chalk lessens your ability to feel and grip the rock surface. You don’t need to coat your hand with chalk and dry it completely. It may seem counter-intuitive but your fingers also need some moisture to be able to effectively grip handholds. If your hands are too dry then your fingers can slip off holds; climbers call this “dry firing.” Some climbers increase moisture on their hands by blowing off excess chalk.