Every now and then we’ll a product that takes the field a huge step ahead of where it was. It may be in safety gear, footwear, or, as was the case with the Mountain Hardwear HyperLamina, sleeping bags. I didn’t fully know that before I began testing the bag — however, with claims like ‘highest performing’ and ‘lightest and warmest,’ I had some seriously high expectations. Now, after a gammut of testing in Montana and Nevada, we are weighing in on the buzz surrounding the HyperLamina Spark.

Mountain Hardwear HyperLamina Spark 35 Features:

  • Engineered to be lightest and warmest synthetic bag available
  • Proprietary welded Lamina™ construction enhances loft and eliminates cold spots
  • Zoned insulation maximizes warmth where it’s needed most
  • Thermal Q® insulation has outstanding compressibility and maintains excellent loft
  • Single #5 half length center zip with dual sliders minimizes weight and still allows for ventilation
  • Performance mummy cut is snug, reducing girth, weight, and bulk and maximizing thermal efficiency
  • Comfort footbox follows natural foot position for maximum warmth and comfort
  • Ultralight shell is soft and highly wind resistant
  • Face gasket and tailored hood comfortably block drafts at the hood opening and seal in warmth
  • Sil-Nylon compression stuff sack and mesh storage sack included
  • Insulation: Thermal Q 60 gram Thermic Micro
  • Bag Shell: 22D Dobby
  • Weight: 1 lb 12 oz / 788 g
  • Bag Fill Weight: 1 lb 4 oz / 567 g
  • MSRP: $220

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It’s light, it’s bright – but is it warm?

The HyperLamina Spark builds upon Mountain Hardwear’s already successful line of synthetic sleeping bags. There are really quite few companies who are offering high-performing synthetic sleeping bags, and on the whole the market is not nearly as competitive as down sleeping bags. For most of the country, that’s perfectly fine – down is generally lighter and more compressible, and modern hydrophobic treatments have mitigated many of the stuff’s age-old woes.

However, for people in the Pacific Northwest, the story is different. I’ve spent entire weeks in the Cascades underneath grey skies and a gentle drizzle. The water seeps slowly into your pack, escaping around or through the cover, and will one day inexorably make its way into your sleeping bag compartment. Perhaps  you’ve wrapped it in waterproof plastic – all well and good, but just wait until you take that puppy out and settle in to a tent that’s spent five days in the rain. Yes, sooner or later, your sleeping bag will get wet if you’re in Washington. At those times, you need a synthetic sleeping bag.

If you’re going with a synthetic bag, the conventional wisdom has been that, compared to a down bag, you’re going to take a hit with regard to size and weight. It’s still true that premiere down bags stuff with 850+ goose down will be lighter and smaller (Mountain Hardwear’s own Speed 32 weighs less than a pound), but those bags also cost hundreds of dollars more. With the HyperLamina Spark, Mountain Hardwear has seriously undermined that notion with a 1lb 12oz total weight that can compete with down offerings from other brands. What’s more, it compresses very well indeed, aided in part by the compression sack that Mountain Hardwear has included.

With that said, let’s now jump in to the bag itself. I begin, somewhat by necessity, with the one thing that everyone notices about the bag first – it is incredibly bright. Mountain Hardwear’s design team chose bright orange and yellow fabrics which are blisteringly bright and impossible to ignore. Frankly, I found them quite annoying until I spent a night in the HyperLamina. I often talk about livability in tents, but the HyperLamina has me thinking that it ought to be a category for sleeping bags too. Frankly, it’s quite delightful to spend a night in such a brightly-colored bag; at night it simply looks warmer and in the mornings the sun makes you feel like you’re wrapped up in cozy tin foil on a campfire. Perhaps that doesn’t sound enjoyable. Anyway, spend a night in the bag and you’ll know what I mean – I think there’s something to be said for bright colors and light fabrics.

Now let’s jump into the technical features of the bag. Its foundation is a 20D nylon treated with a DWR to fend off moisture. It’s a light fabric with an exceptionally smooth handle. I should note that I’ve treated my sleeping pad with silicone dots, otherwise I imagine this pad would be especially prone to sliding off the pad in the night.

A look at the shock cord closures around the face

A look at the shock cord closures around the face

The insulation is Mountain Hardwear’s proprietary Thermal Q Thermic Micro. This is one of a new generation of synthetic insulations that are designed to mimic the structure of goosedown, with a firmer ‘quill’ that supports light, airy strands of fiber to create loft. Ounce for ounce it’s not as good as goose down, but compared to synthetic competition it’s very light and compresses well.

Another defining feature of the bag is its front #5 half-length zipper. There’s really only one benefit to a half zipper – that it’s lighter – and there are a number of drawbacks. It can make getting into the bag harder and you can no longer vent your feet. However, for a bag that’s aiming to be ultralight, this is the right choice. What’s more, Mountain Hardwear made it a two-way zipper, so you can still vent from around your waist. The zipper has a full-length draft tube that comes complete with velcro tabs to either secure it in place or out of the way for easier zipping and venting.

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Note the zipper garage and large, easily grasped zipper pull

The performance of this draft tube is important. Theoretically, a top-mounted zipper stands to leak more heat than a traditional one on the side, simply because warm air rises. So, although the velcro tabs feel out of place inside of a sleeping bag, it was a good call on Mountain Hardwear’s part because they ensure a tight seal. The velcro tabs perform an important function because they can help keep the draft tube out of the way of the zipper, which does tend to snag fairly easily.

I’ll conclude with a look at the HyperLamina’s hood design. I’m uncompromising when it comes to this part of the sleeping bag – if you’re going to spend a night in the cold, you want the area around your face to be warm and comfortable. Mountain Hardwear included twin shock cord adjustments to cinch the bag around your face for a good seal. They did a good job with the design, which manages to get a reasonably good seal (for a summer bag) while not permitting the shock cord to press into your skin. The face gasket isn’t especially sophisticate, but for a summer bag the existing design is perfectly functional.

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The overall performance is nicely illustrated by an ideal testing night that I had while back in Nevada. I was camped out on a bank of Lamoille Creek around 7,000 feet. For testing purposes I wore my very lightest layer, nothing more than ultralight summer polyester, to get a sense of the bag’s temperature limit. Well, around 4:00 in the morning I woke up slightly cold. I looked at my watch’s thermometer and, lo and behold, the temperature was 32 degrees. I quickly put on a more realistic sleeping layer (light merino) and was easily warm enough to sleep comfortably. So, since the HyperLamina’s comfort rating is 32 degrees, I was very impressed with its warmth. My initial layer wasn’t realistic and I only chose it to test the bag – in my normal sleeping layer, I imagine that I could have pushed the bag comfortably down into the high 20’s.

The HyperLamina achieves this warmth-to-weight ratio using zoned insulation, so there’s less of it beneath you and relatively more in the generous footbox. Intentional design touches like these are the foundation of a bag that legitimizes its manufacturer’s lofty claims.

The Good

  • Excellent warmth-to-weight ratio for a synthetic bag
  • Very light overall, pushing into down’s territory
  • Feature set is present and correct – good zipper, comfy hood and good draft tube
  • I’m rather fond of the fabric colors, despite initially hating them

The Bad

  • Velcro tabs on draft tube feel out of place and a little cheap
  • Zipper tack lacks any substantial anti-snag

The Bottom Line: HyperLamina Spark 35

There’s no doubt in my mind that the HyperLamina Spark is the best synthetic bag on the market. It’s very light and still manages to be completely true to its temperature rating, something few synthetic bags seem to nail. I like the careful feature set and, I must say, I always slept well in the bag. Doesn’t that say it all?

Buy Now: Available from REI.com

About Author

Kevin Glover is an outdoorsman living, climbing and biking in Spokane, WA. Originally from the Nevada high desert, he moved to the PNW for its mild winters and allergen-free summers. He has guided throughout the Cascades and Enchantments for Peak 7 Adventures.

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