The Hyperlamina Spark 35 is rated at 35°F for their US market, despite being labeled as a 32°F on most of its attached literature (and its storage and compression sack). This is because it has an EU Temperature Limit of 32F (or the EU's Men's Temperature Rating). Overall, we found that this bag was pretty average in warmth among both 35°F synthetic or down bags. In our side-by-side testing, the Spark 35 wasn't as warm as any of the 30°F models, but also wasn't FAR colder than most 35°F models.
We do think if your body temperature runs low, this bag might only be good to 40°. Mountain Hardwear uses an insulation called Thermal Q, with a 60-gram layer. What does that mean? Thermal Q is a proprietary insulation made by Mountain Hardwear and used in several models of their sleeping bags and jackets. It is one of the lighter and more compressible synthetic fabrics but is slightly less long lasting than other synthetic materials.
If you're after a warmest synthetic bag be sure to check out the new The North Face Hyper Cat which is rated to 20°F and while not super warm for its temperature rating is noticeably warmer than the Spark. The 30°F Western Mountaineering Megalite and the Patagonia 850 Down 30 are both warmer, lighter and slightly more compressible down options.
At 1 pound 12 ounces, the Spark 35 is one of the lightest synthetic bags on the market for its temperature rating. If you frequently camp in wet environments, where it would be best to take a synthetic bag then the Spark is though to beat. It is worth noting that The North Face Hyper Cat is only 2 ounces heavier, though the Spark is far lighter than most other synthetic models including the mega classic 20-degree Cat's Meow (2 lbs 5 oz). The REI Co-op Igneo 25 is similar in price, but is down, and weighs 1 pound 10 ounces.
Part of the reason the Hyperlamina is so light is its high-quality synthetic fill, fairly low-weight 22D nylon shell, and half-length zipper; the zipper shaves 2-3 ounces off versus using a full-length zipper. Even compared with closely rated down bags, the Spark 35 doesn't give up much; in fact, it's lighter than the Kelty Cosmic. Basically, it's one of the lightest 30-35°F synthetic bags that are currently available.
Besides being one of the lightest synthetic bags, the Spark 35 is also easily one of the most packable options (of its temperature rating) on the market today. Check out the chart below to see where this bag scored in Packed Size compared to its competition.
The Spark 35 packs down smaller than several down bags like the Kelty Cosmic Down 20, and is even comparable to performance-oriented bags like the Western Mountaineering MegaLite, Patagonia 850 Down 30, and Marmot Phase 20, though it's around 15-20% bigger than those models. The Hyperlamina Spark 35 is definitely smaller than the The North Face Cat's Meow, but less so with the 2018 update to the Meow..
We love that the Hyperlamina Spark 35 comes with a very functional compression sack, in addition to the storage sack. The compression sack fits the bag very nicely and helps to minimize the amount of space that this bag will take up in your pack.
The Spark 35 offers wider than average dimensions compared with most backpacking-oriented mummy-style bags in our review and on the market including the Hyper Cat. It offers near identical dimensions as our Editors' Choice the Western Mountaineering MegaLite and was one of the more comfortable bags that we tested. While it offered fairly spacious dimensions, we never felt like the bag was too big; in the case of a bag being too big, cold spots have the potential to be created. We did not face this issue when using the Spark.
Most side and tummy sleepers could get their knee pretty high while sleeping in this bag. We found it to offer a high level of comfort among contenders we tested, especially for those who sleep in positions other than on their back. The Spark 35 features a comfortable 22D fabric for its lining, which was above average for its feeling against our skin. We liked the interior fabric of the Spark 35 better than the Cat's Meow.
This is a fairly versatile bag. It's spacious enough for car-camping, light enough for most backpacking trips, and its synthetic fill helps it excel in both wet and dry climates. The half-zipper offered plenty of ventilation; slightly to our surprise, we never felt it was a hindrance during our real-world testing.
We do think that in warmer weather, the Hyperlamina might be a bit more difficult to use as a blanket, as you can't open it all the way up. In temperatures that dip below 35°F, the Spark offers plenty of shoulder space, which allows the user to wear additional layers. The Western Mountaineering Megalite and Ultralite were some of the most versatile bags in our review.
The Hyperlamina doesn't have a lot of extra features, as its design focuses on low weight and compressibility. Its half-length zipper shaves off a few extra ounces and we enjoyed that it was in the middle, versus having a less useful zipper of the same length on the side. We hadn't used many center zip style sleeping bags previously and were a little skeptical; however, after several days in the field, nearly all of our testers loved the design. It's just plain easier to unzip, sit up in, and perform daily activities in. The hood is basic, yet well-designed, and is effective and comfortable. The Sea to Summit Spark III offered more features and a better overall design.
The synthetic fabric used in the Hyperlamina is super lightweight and compressible, but is slightly less durable than other synthetic fabric; it will likely lose around 20% of its warmth when you hit the five-year use mark.
Water-resistance and drying times were pretty similar for the treated and non-treated down bags we tested. Synthetic fabrics performed far better, taking about 20% off the times of hydrophobic down in the soak test.
The Spark 35 is probably the best summertime 3-season backpacking synthetic bag we have seen. We remain amazed by its low weight and fantastic packed size, as it's comparable to average and slightly above average down bags in many ways. If you want a warmer bag to use regularly around 30°F and below, we'd go for Hyper Cat for backpacking or climbing or The Cats' Meow for occasionally backpacking or car camping trips as both are noticeably warmer and rated to 20°F.
At $220, the Hyperlamina Spark 35 is comparable in weight and packed size to that of many down bags with 700+ or lower down fill power. That said, it is also comparable in price to many of those bags and it likely won't last as long, because synthetic fibers break down far quicker (than down), losing their warmth.
