Sterling Ion R 9.4 XEROS rope: Every filament is dry-treated and made for the alpine

When my partner and I began prepping for a Grand Traverse attempt in the Tetons this summer, he asked if there was any way we could take a 60-meter rope instead of a 70-meter to save on weight and bulk. Maybe we could get away with a carabiner block, or a tagline for the longer rappels, he suggested.

No need: I had a Sterling Ion R 9.4 XEROS. Now my alpine rope of choice, the Ion R weighs 57 grams per meter, making it about 0.3 pounds lighter than other 70-meter ropes I’ve tried in a similar diameter range. A tight, dense weave also makes it feel more svelte: I scarcely noticed the difference between the Ion R and Sterling’s notoriously slender Nano IX 9.0.

Of course, that’s all first impression. As the saying goes, it’s what’s on the inside that counts. In this case, it’s Sterling’s innovative new dry treatment technology that really makes the Ion R XEROS worth its weight. (“XEROS” is Sterling’s term for this uniquely comprehensive approach to dry treatment.)

To explain the benefits of this treatment, let’s start off with a refresher on a rope’s components and why dry treatments are important for lines that are likely to be exposed to rain, snow and water.

Rope anatomy: The colorful outer layer, the sheath, surrounds and protects the rope’s core. That core is made of a twist of thick white yarns, and each yarn is composed of dozens of tiny, hair-thin threads called filaments. I’ll get back to that in a moment.

Why is it sometimes important to have a dry-treated rope? Sterling’s website indicates that “rope loses 20% to 40% of its strength when wet,” and a 2012 article in Climbing reports that waterlogged ropes can lose up to 70 percent of their dynamic strength. The other issue is that wet ropes are heavy, prone to freezing and a pain to belay with and coil. When the UIAA announced a new certification standard for dry-treated ropes in 2014, the organization cited findings that an untreated line could absorb up to 50 percent of its weight in water, and even some dry ropes absorbed as much as 40% of their weight. Currently, dry ropes that are certified by the UIAA absorb no more than 5%. (A 2015 blog post by Alison Dennis on Weigh My Rack analyzes the UIAA’s testing and labeling practices for dry ropes.) The Sterling XEROS is UIAA certified.

Now, here’s the idea behind the XEROS dry treatment. The Sterling website explains that, historically, ropes have been dry-treated by dunking the finished rope in a chemical bath, leaving a thick, water-resistant residue on the sheath. Sterling’s XEROS treatment involves treating each individual filament. Their website says, “What we’ve created is not a coating applied to the rope, or a separate liquid bath treatment. It’s a new step in the manufacturing process of individual nylon fibers, before they’re even twisted into yarn, that makes each fiber water resistant.” Sterling also claims that the new practice reduces waste, energy use and labor, making it better for the environment.

There appear to be multiple advantages to this approach. For starters, the traditional chemical-bath coating generally wears away over time, making those ropes more vulnerable to soaking after just a season or two. By building ropes with treated filaments, the XEROS ropes seem more likely to hold up over time, not just in terms of water resistance but also against wear and tear. As the Weigh My Rack blog explains, dry-treated ropes have generally proven to have greater durability than non-treated ropes. In this case with the Sterling XEROS treatment, having that level of protection to every filament seems like it would add longevity.

Meanwhile, treating each filament leaves a thinner, more even coating on each individual thread, rather than a thick, gummy outer layer. If you’ve used a new dry rope before, you know fresh treatments can attract dirt like white slacks at a rodeo. With the Ion R 9.4 XEROS, I never had that problem. I roughed it up on granite sport climbs and dusty multipitch trad routes in Colorado’s Front Range all summer. Even after all that use, the Ion R still ran through slushy late-season snow, rivulets of runoff, and wet chimneys in the Tetons without taking on any water. (Climbers should remember, however, that even when the rope filaments are non-absorbent, it’s still possible for moisture to work its way into the empty spaces between filaments. Which is to say that it’s still possible for even the best dry-treated ropes to succumb to the effects of water.)

I also appreciated the rope’s feel: slick, but not sticky. Because of that natural slickness and the tight sheath, it ran easily through low-angle terrain without catching on rough stone. I experienced noticeably less rope drag than I’d expect to encounter with other ropes. So far, the sheath still looks like new.

The dense weave and apparent durability do come at a small cost. The Ion R 9.4 handles more stiffly than either the Sterling Nano IX or Sterling’s previous edition of the dry-treated Ion R. The stiffness was nice for clipping but not always ideal for quickly saddle-bagging the rope or managing coils at hanging belays. To be fair, the Ion R 9.4 XEROS is no stiffer than other dry-treated ropes I’ve used. Still, if you prefer buttery, supple handling and are on the fence about purchasing a dry rope, the Ion R 9.4 might not be for you.

Five stars: Overall, the Ion R 9.4 XEROS leaves little room for complaint. While I haven’t been using the rope long enough to vouch for its long-term durability, the new XEROS technology exceeds expectations on all counts so far. If you’re looking for a rope that’s meticulously dry-treated and reliable in all conditions, the Ion R 9.4 XEROS is a safe bet.

Corey Buhay is a writer and editor based in Boulder, Colorado. She has been a member of the US Ice Climbing Team since 2018.

Pros
Lightweight (57 g/m)
Tight sheath defends against dirt
Firm handle makes for easy clipping
Middle-marked
Slick texture minimizes rope drag
Dry treatment is permanent
No gummy feel from chemical coating

Cons
Handles more stiffly than non-dry treated ropes
Potentially costlier than untreated ropes