Chalk it up

If you’re worried about returning to the climbing gym or crag for fear of touching the same holds hundreds of others have touched, hold onto your harnesses. Researchers at CU have found that climbing chalk kills the coronavirus.  

But don’t go grabbing for any old chalk. The magical virus-killing properties apply only to 80-percent ethanol liquid chalk. For the study, a team at the University of Colorado tested “Secret Stuff Hygienic” liquid chalk, made by Denver-based Friction Labs. 

Lead author on the study was professor of immunology Ross Kedl, also an avid climber. He became intrigued when he received an e-mail from Friction touting its 80-percent ethanol Secret Stuff Hygienic and decided to put it to the test.

Kedl, along with his team, started by wiping sterile swabs on unchalked hands and hands covered in Friction Labs’ liquid chalk. Samples were then sent off to the petri dishes, with the chalk samples coming up clean after 24 hours.

Next, they tested the chalk against the actual coronavirus, SARS-CoV-2, which they had access to in a biosafety unit. (Do NOT try this at home.) For this test, the team applied the virus to plastic film and let it dry. They applied the 80-percent ethanol liquid chalk to the film and tested immediately and after five minutes. Within seconds, 99 percent of the virus was gone. After five minutes, 100 percent was gone. They also performed the test using nothing and a sterilizing agent.

Although the test proved the efficacy of 80-percent ethanol liquid chalk, Kedl warned against using anything lower than 65 percent. “You're not going to be sterilizing," he said. It's also important to note that 80-percent ethanol liquid chalk doesn't provide lasting protection. Instead, think of it like hand sanitizer. If you apply it at the base of a route, you'll need to apply it after lowering to kill anything you'd picked up along the way.

Nevertheless, the news should help ease  minds. "If you have a gym full of people who are wearing masks and using this chalk, your chances of getting a wall contaminated with coronavirus are pretty small," said Kedl.

Kedl's team isn't the only group testing chalk's role in preventing COVID-19's spread. The Association of British Climbing Walls published a report last week that found standard climbing chalk also was effective in reducing the virus on a hold by 99 percent. The British team was not able to use the actual SARS-CoV-2 virus, instead substituting a closely related coronavirus. They put samples of the virus on plastic meant to mimic climbing holds and saw a 99 percent reduction of virus within one hour. “We are really pleased that the findings suggest chalk powder is ... unlikely to harbour coronaviruses,” virologist Maitreyi Shivkumar said.