Because Science

This 2020 Sleeping Bag Is Warmer and Lighter — Thanks to Titanium?


Key Specs:
Brand: Rab
Model: Mythic Ultra Sleeping Bag
Price: $550 for the 32-degree model, $650 for the 18-degree model
Availability: Spring 2020
Unique Features: Liner fabric coated with titanium at the fiber level to increase warmth without affecting weight.

Upshot: When outdoor gear makers equip sleeping bags with new innovations, it typically results in a sack that’s lighter, warmer or, in many cases, both. That’s true for Rab’s forthcoming Mythic Ultra sleeping bags, which use a new fabric technology to, according to the brand, increase warmth by 32 percent without increasing weight. The Mythic Ultra will be available in two models, one rated to 32 degrees Fahrenheit and another rated to 18.

Who It’s For: Campers who want to lighten their load.

Insight: The breakthrough tech that Rab is using in the Mythic Ultra is called TILT, which stands for Thermo Ionic Lining Technology. Visually, TILT appears to manifest as a liner that’s coated with a reflective element like foil, which we’ve seen before in apparel (Columbia’s Omni-Heat is one example). But that’s not actually what’s happening here; TILT fabric is coated at the fiber level with titanium through a complicated process involving a vacuum, ions and more chemistry than we’ll get into here.

The result is that the Mythic Ultra bags are, depending on the model, roughly seven to 14 degrees warmer than sleeping bags with similar construction but no TILT liner. The temperature ratings mentioned above don’t reflect this increase because radiant heat loss, which is what TILT cuts down, isn’t measured during standard sleeping bag temperature tests. In other words, each of the Mythic Ultra bags will actually be warmer than their rating lets on — by no insignificant amount, either.

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