When was the last time you made butter and ran simultaneously? This is the question Libby Cope, 30, an Oregon-based outdoor and running content creator, asks in a video that has racked up more than 2 million views on TikTok and nearly 10 million on Instagram.
She and her boyfriend, Jacob Arnold, 30, a sterile processing tech at a hospital and an avid runner and biker, do just that: they pour heavy cream and salt into double-bagged Ziplocs and secure the squishy bags of dairy inside their matching running vests before setting off on a trail run. At the end, they spread their creation on sandwich bread and dig in.
Cope, known on Instagram as @lib_claire and @momcallsmebirdy on TikTok, told Runner’s World over Zoom that although she’s been a full-time content creator for a while now, this is her first truly viral video—which is fitting, because she loves dairy. “I used to be vegan, but you can’t get good butter as a vegan,” she said.
In fact, Cope’s love for high-quality milk was actually what gave the couple the idea for their churn-run. About a month ago, she treated herself to a bottle of cream-top milk from Alexandre Family Farms to put in her coffee. Noticing how easily the thick liquid foamed up when shaken, Arnold wondered aloud whether, if he took it on a run, it would turn into butter.
Could they, theoretically, make butter by running?Cope was game to try it and find out, especially because the great outdoors has long been her favorite kitchen. “I actually prefer cooking outside over my own apartment,” she said. “I love cooking on a camp stove. It’s so much more exciting.”
She and Arnold Googled whether it was possible to make butter in a bag, a technique she vaguely remembered from high school, and found out it was. Then they searched whether it was possible to do so by putting the bag in your running vest and going on a run. Although the AI overview affirmed such a thing was possible, they found no web results indicating anyone had tried it before.
Cope and Arnold in the lab
How is this possible?
Let’s pause for an extremely basic butter-making lesson, courtesy of the Center for Dairy Research. Oil and water can’t mix unless they’re emulsified, and milk itself is an emulsion that slowly begins to separate after it sits for a while, with the fattier molecules floating to the top. The section of highly fatty milk that gets skimmed off the top is what we know as cream, and when cream is agitated, or churned, or generally shaken really hard, the fat molecules floating around will start finding each other and sticking together, expelling many (but not all) of the liquid molecules to the outskirts—and forming butter.
Running for the butter
In their initial, viral attempt, Cope and Arnold used a total of four pints of heavy cream, which Arnold said was, in retrospect, far too much. “We both had 32 ounces of heavy cream in our vests, and that was a little bit extreme,” he said. They were also worried that the body heat from their backs would disrupt the process, so they stopped to cool the bags in the river during their run. “It was probably 40 degrees outside, but there’s a lot of heat going on in the back,” said Cope.
But putting their baggies in the river actually slowed the process down. This tracks with the science; according to Scientific American, room-temperature cream turns to butter much faster than cold cream because the molecules move more quickly at higher temperatures. Of course, if the temperature gets too high, everything will just melt, so their experiment probably wouldn’t have worked on a summer run. All in all, Cope and Arnold said they ran for a total of about an hour, although the actual process took longer because they kept stopping to check on their butter.
After posting the first video, Cope and Arnold refined their process for a second attempt. That try was even more successful, with the cream turning to butter much more quickly, which Cope attributed to the higher quality cream they used, the more strenuous trail, and the fact that it was a little warmer outside. “I’d say 50 degrees, 55, is pretty ideal conditions,” said Arnold.
Now, the couple has more butter than they know what to do with. “We’ve consumed an alarming amount of dairy over the last week,” said Arnold. And while their taste buds are thrilled with the situation, Cope’s skin is not. “Yeah, I’m breaking out,” she said.
Already, Cope's video has inspired other runners to try churn-running, like Irene Choi, who made corn juice honey butter, and Lauren Lecompte, who tried making her butter during a snowstorm but had to follow up her run with some at-home churning because of the cold temperatures. And Cope was quick to point out that, since posting her video, she’s learned about the runner TrailswithZach, who has made both chocolate ice cream andfrosted lemonade while running.
For Cope, the experience has been a grounding reminder of why she runs in the first place: the joy it brings her. “Sometimes it’s easy to forget what you’re doing it for, and it’s not for a bunch of medals and all that,” she said. “It’s just for the vibes. Just the butter.”
Katja Vujić is a freelance writer based in Brooklyn whose work has appeared in Runner’s World, The Cut, Allure, Architectural Digest, The Boston Globe Magazine, and more. You can find more of her work on her website.