What's the point of chalk for bouldering? What's the difference between loose and ball chalk? Are there any alternatives? John Gaskins tells you all you need to know about chalk.
Bouldering techniques - chalking
The idea behind chalking your hands is for the chalk to absorb the sweat excreted through your fingers, thus effectively drying your fingers and giving you a better grip on the holds. The aim is to have a fine layer of chalk on both your hands and the holds, so it's best to lightly chalk all the holds prior to attempting any problem. This may require tactics such as using an extension pole to brush chalk on to holds.
The aim is to have a fine layer of chalk on both your hands and the holds
Chalk itself can be loose (in a block that can be broken up) or in a mesh ball. To minimise dust, climbing walls commonly require the latter. However, it is often very difficult to 'chalk up' properly with chalk balls when on a problem. In contrast, with block chalk, dipping into your chalk bag will automatically get chalk on your hand.
An alternative for mid-problem chalking up is to use 'megagrip' liquid either as a base layer or instead of chalk. This is applied thinly to the fingers and allowed to dry: it is particularly good on longer problems.
A further option is to over chalk jugs so that the excess can be rubbed on to your hands at that point.
Chalk is also increasingly being used to draw lines to holds. This practise is both unsightly and unnecessary. Small tick marks may occasionally be useful for blind holds although they should be removed prior to leaving the crag.