You’ve probably seen it on a climber’s leg, smeared on their face, or scattered on the crash pad, small powder flakes in white. That’s chalk - calcium carbonate - a (sweaty) climber’s best friend. Chalking up your hands absorbs the sweat from your hands, dries fingers and palms which allows better grip, and generally improves the friction between your hand the hold.
There is a long history of using chalk in sports, especially gymnastics. The first known climber to adopt using chalk was John Gill at around 1954. He used to be a gymnast and he had an idea that if chalk works for gymnasts, it can very well work for climbers. Within one decade, people started smearing that stuff on climbing crags worldwide. Until today, there has been an ongoing discussion about whether chalk is cheating or not. Few outdoor crags have use of chalk still banned as they are the last "traditional" crags, mostly on sandstones in Nother Bohemia and German Saxony. But in general, chalk was adopted all over the industry and everybody uses these days.
There’s also a thing called the language of chalk. For climbers that are trying a new route, especially on-sights outdoors, they can more easily identify the holds they want to use. They’ll go for by checking if it still has marks of the excess chalk left by previous climbers. This helps you immensely if you can read it well, as finding holds outside is never an easy job.
Some climbers consider it wrong to use chalk since you’re leaving traces on the wall. So be a nice climber and make sure that you clean all the holds using a brush, especially tick marks (marks highlighting a specific place on a hold that you want to use) once you are done with the climb. Anyway, chalk has been more than beneficial for climbers alike and it comes in many different forms.
Blocks of chalk: compressed calcium carbonate in a rectangular shape. It is usually sold as blocks of 50-60 grams. You can crush it into smaller parts once you put it into a chalk bag. Good thing is that it can last longer than powdered chalk as the bigger pieces are less likely to fly off from the chalk bag.
Loose chalk: chalk broken down to small pieces and chalk dust. It can be either very fine or with some bigger pieces. It is usually sold in boxes of 100-250 grams, a little cheaper by weight than blocks. The downside is that loose chalk tends to fly/fall off the chalk bag and the overall consumption is thus significantly higher than using blocks. One way to tackle this problem is the use of a chalk ball. Not everyone loves the huge chalk clouds hanging in the air in the gyms.
Chalk balls: a mesh cloth in the form of a ball filled with loose, fine chalk. It is tightly fastened and put into a chalk bag. Since it’s in a ball shape, it allows for easy grabbing. The ball can be either single-use or refillable. This is the most efficient way of using chalk as there is very little chalk to be released through the fabric. But not all climbers prefer this way as some prefer bigger amounts of chalk to be used at once.
Liquid chalk: the least famous, but not necessarily the least preferred. Chalk is kept in a fluid form by the addition of alcohol, which evaporates quickly once it gets into contact with skin. It is sold in a small bottle of 100-250 ml. Some climbers prefer liquid chalk as there are no dust clouds at all and the evaporating alcohol tends to dry the hands very well. Some climbers use a combination of both - first you put on liquid chalk before the climb and during the climb, you use a normal chalk bag.
There’s no superior chalk type since it all depends on preference and form of climbing you practice. Just get yourself well acquainted with the types and choose your weapon. There are many brands out there and some elite climbers claim to be able to differentiate which brands are better. To be honest, just try a few and make your mind about which one you prefer. You wouldn’t want a slippery hand preventing you from finishing your route!