Climbers use chalk or magnesium carbonate (MgCO3) as a drying agent, like gymnasts and weightlifters, to keep their hands dry and secure on small handholds. Chalk often improves your grip on rock surfaces, especially when air temperatures are hot and your hands are sweating.
Climbing chalk can be purchased in four different types: blocks of gymnast chalk; powdered chalk; chalk-filled fabric balls; and liquid chalk.
Blocks and Crush of Chalk
If you took gymnastics or weightlifting in high school gym class then you probably remember using blocks of chalk or magnesium carbonate to keep your hands dry. Since John Gill, a former gymnast and the father of modern bouldering first introduced gymnastic chalk to climbing back in the 1950s, climbers have used rectangular 2-ounce blocks of chalk to keep their hands dry. One of the most popular block bands is Endo chalk.
The blocks, composed simply of pure magnesium carbonate without additives, usually come in packs of eight that weigh a pound total although most climbing stores will sell a single individually-wrapped block for a buck or so apiece. Buy a block of chalk and crumble and crush it in your chalk bag. Instead of putting the whole block in your bag, put half in the chalk bag and the other uncrushed half in a zip-lock plastic baggie, which you can keep in your pack to replenish the bag as you use the chalk up.
Climbers can buy powdered chalk that is already crushed into a fine dust, which is then easily poured into chalk bags. Powdered chalk is often specifically formulated for rock climbing by manufacturers like Metolius with drying agents to increase hand dryness and perhaps create a better grip on holds. Powdered chalk, however, is more expensive than blocks of chalk. It can be messy and easily spills out of your chalk bag, so don't overfill it.
Many indoor climbing gyms do not allow climbers to use powdered chalk since fine chalk dust lingers in the air, clogging both climbers’ lungs as well as the gym's ventilation system. Powdered chalk comes in durable, sealable bags or bottles, with packages usually weighing between 4 ounces and one pound.
Chalk balls are small sacks made of a porous mesh material that is filled with powdered chalk and then sewn shut. Chalk balls are definitely the best type of chalk to use for indoor trainingat climbing gyms. Many indoor climbing gyms require chalk balls rather than loose chalk since the chalk is easily applied to a climber’s hands, chalk dust is minimized in the air, and chalk is less easily spilled on the floor.
It is sometimes difficult to completely coat your hands with chalk from a ball but it’s usually not a problem in gyms since most routes are short. Some climbers use a chalk ball when climbing outside but also add loose chalk to their bag so that they can dip their hands and get a complete chalk coating. Chalk balls also last longer than loose chalk since the chalk is contained and you tend to use less of the white stuff. To use, just put the ball in your chalk bag.
Liquid chalk, such as Mammut Liquid Chalk, is a specialty chalk product specially designed for climbers in gyms or indoor facilities. Liquid chalk is simply squirted onto your palms, spread all over your hands and fingers, and then allowed to dry. After the alcohol in the chalk dries, a dry white base layer of chalk covers your hands. Liquid chalk is best applied before a climbing or bouldering session. Most climbers also use a minimal amount of regular gymnastic chalk along with the liquid stuff while climbing.
Liquid chalk is easy to apply, lasts longer than regular chalk, avoids clouds of white dust, and actually works well since it minimizes the number of times you dip your fingers into your chalk bag. Liquid chalk also leaves less residue on the rock or indoor wall than regular chalk and, since it lasts longer on the hands than regular gymnastic chalk, a climber dips his fingers into his chalk bag less often, which could make a difference in climbing competitions or redpoint attempts on a hard route.