We’ve all seen it at the local crag, maybe in the climbing gym or high on an alpine route. Johnny rope-gun gets to the crux of the route, palms sweating from the heat and exertion. He digs into his chalk bag to dry them off before tackling the move. But is all that rock marking chalk helping him? Some say (and have proven) not. In addition, covering your hands in chalk actually reduces the friction your fingers have on rock.
The testing rig.
Yeah I know…try telling Tommy Caldwell that (or anyone at the City of Rocks this weekend) as he’s chalking up for his next speed ascent of El Cap. It’s hard to believe, but the University of Birmingham, UK, did a pretty thorough study (Use of Chalk in Rock Climbing: Sine Qua Non or Myth) of the factors involved in 2001 and came to the conclusion that chalk lowered the coefficient of friction by about 18% (COF: no-chalk=3.00, chalk=2.46). The theory is that chalk creates a granular layer in which the small smooth particles roll on each other…therefore reducing friction.
Whether wet or dry, the use of chalk reduced the amount of friction.
The study went on even further and tested the effects of wet hands, with and without chalk, as well as on different types of rock (granite, sandstone, slate), with the results continuing to support the fact that chalk may be better left at home. While the chalk did help to dry the hands, any residual chalk left on them reduced friction. The study concludes that dry, clean hands offered the most grip and that a towel, instead of a chalk bag, may be better suited for the back of your climbing harness.