Testing frozen ropes is one of the most frequent requests we get at HowNot2. In our endless pursuits to answer all of your questions we froze semi-static, dynamic, dry treated, and non-dry treated ropes into blocks of ice and broke them. These are the lengths we go to for science!
We soaked 8 rope samples in water. Half the samples were then frozen into a block of ice at their center, the rest were frozen in a knot. We also broke four control samples so we could compare the results.
The dynamic rope was a dry treated 9.8mm Sterling Velocity with 28.8% elongation and is 62g/m rated for 6 UIAA falls. You can find that here.
The semi-static rope was non-dry-treated, 10.0 Beal Spelenium with a static elongation of 4.1%. You can find that here
Freezing your ropes makes them stronger! Start storing your ropes popsicles. Just kidding, all samples broke at basically the same force and in the knot, like ropes pretty much always do in our tests. In short, Ice did not affect the strength of our rope samples.
More Issues Than Just Strength
Strength is only one factor. Frozen ropes are a big problem in actual use. Ice makes ropes heavier, stiffer, and more difficult to handle. It can interfere with ascenders, belay devices, progress captures, and prusiks. Belaying and rappelling can become difficult, dangerous, and sometimes impossible. Ropes can freeze into ice, making them impossible to recover. Icy ropes can lose their dynamic properties, resulting in hard catches and high impact forces on protection.
Don't Let It Get Icy, But If You Do...
Luckily, there are some tactics to prevent a rope from freezing. Dry treatment helps ropes absorb less water, shed new ice buildup, and remain less stiff. Keeping a rope moving will prevent it from freezing into ice. Not letting the rope get wet on the approach helps. Avoiding running water and seeping areas of a climb help tremendously. Bringing a rope into your tent can help prevent freezing on overnight trips.
In some conditions, ropes will ice up no matter what you do. It helps to use rope a skinny diameter rope on the small end of the range that your belay device is rated for. "Snapping" the rope as you belay and "flossing" it through the belay device will help it soften so it feeds better when belaying. On rappels, a munter hitch or even a Dulfersitz (body belay) may work better than a belay device.
We hope this article helps you understand the effects of ice on climbing ropes. We thrive on your questions and comments, so if we missed something post your comments on the youtube video and we will investigate.
Feedback from Comments
Several people were concerned we didn't soak the rope long enough so the rope wasn't saturated and therefore the ice was only on the outside of the rope. We tested wet ropes also and with dry-treated or non-dry-treated ropes, we found that they would be fully saturated the water could fully turn to ice so we believe they were saturated and solid ice during the tests.
Rumor has it that nylon gets weaker when it's wet. Even your climbing ropes have warning labels about it. We tested it thoroughly and we think you should look at what we found.