In the mid-1950s gymnasts like soon-to-be prolific boulder-problem-solver John Gill controversially introduced gymnastics chalk to rock climbing. Today the use of chalk in climbing is ubiquitous, though its visual impact on natural cliffs is still a topic of debate. Interestingly, the climbing chalk we use on our hands today isn’t actually chalk, which in reality is a sedimentary rock made up of calcite, or calcium carbonate. For that matter, the chalk for a chalkboard isn’t chalk either; it’s gypsum. But for the sake of simplicity, we and everybody else will continue to refer to it as chalk, which brings us to what you’ve come to learn: How to choose the best chalk for climbing.
Types of Chalk: Most climbing chalk is pure magnesium carbonate, available in blocks, as a powder, or in small cotton balls intended to reduce spillage.
Balls versus loose chalk: Chalk balls are preferred by many broke climbers because it extends the life of the chalk. Some really broke climbers may actually use an old sock, which is nasty. Many climbers, especially those who climb in hot climates, prefer the feel and generous delivery of a chalk bag full of loose chalk.
Drying Agents and colored: Some companies blend their chalk “drying agents”, the exact ingredients of which aren’t detailed, but are probably antiperspirants like aluminum trychlorohydrex, which plug up sweat glands temporarily. Many people swear by these “supercharged” chalks, while some people don’t seem to have a preference at all. Some chalk is available specially colored to match the rock for those who hate the look of tick marks, and in some sensitive areas, climbing chalk isn’t even allowed.
Liquid Chalk: For people with particularly sweaty hands, the use of liquid chalk is highly recommended. Often a blend of chalk, antiperspirants, and hydrophobic compounds or rosin, these act as a highly effective base layer of chalk over which traditional powder chalk can be applied.
Chalk alternatives: Chalk alternatives are usually antiperspirant and hydrophobic compounds that dry your hands without leaving marks on the rock. The ingredients in these do not require disclosure, so consistency between brands varies widely. They are available in both liquid and powdered form, and are sometimes marketed to other activites like golf and tennis.
In certain areas like Fontainebleau in France, the uniquely slippery rock led local climbers to eschew magnesium carbonate and use a local material called pof, which is dried pine resin that increases the friction of the holds. This practice is not used in the majority of the climbing world, and should be avoided, as it can lead to making holds slippery in different types of rock.