After a lot of side-by-side testing with all the other models in our review, the Black Diamond Mercury Mitt proved to be the straight-up warmest model we tested. The Hestra Army Leather 3-Finger was close, but the Mercury proved to keep the most heat in overall. The Mercury was also the most water-resistant, and among the most durable, its only drawback..? Dexterity, which was pretty much the poorest overall.
The Mercury Mitt uses 340 grams of PrimaLoft Gold insulation, plus a warm-to-the-touch, high-loft fleece. The result was the warmest overall glove or mitten in our review. It ties with the Capstone, but that glove uses electricity. When the batteries run out, and you don't have a spare, the Mercury is much warmer. We have used these mittens down to -10F, and while we wouldn't want to use them in much colder temperatures, they worked as well as you could hope in those conditions. The Mercurys don't have Denali-worthy warmth, but they aren't far from it and are warm enough for the slowest and coldest of East Coast or Mid-West chairlift rides or snowmobiling.
As you might guess with all that insulation, the Mercury Mitt didn't have excellent dexterity and was overall one of the poorest performing products we tested for performing tasks that require fine motor skills. They do feature an optional trigger finger sleeve in their liner to increase dexterity. This sleeve helped our "feel" and made these mitts feel marginally less clumsy; however, in our testing, this sleeve only slightly improved dexterity at tasks that required nimbleness. The reason it's "optional" is because you don't have to use it. Due to Black Diamond's design, the other side of the index slot has enough space for all four of your fingers so you can keep them next to each other for improved warmth, but overall we thought this likely made this glove offer poorer dexterity and "feel."
In our side-by-side testing, we could perform basic tasks like buckling ski boots, and zipping jackets with big zipper pulls. For more complex tasks, these mitts were challenged. We didn't think the Mercury's dexterity was anywhere near as solid as the Hestra Army Leather 3-Finger Mitt.
The Mercury Mitt performed well in this metric, though it did not offer amazing performance in wet conditions. The shell itself is pretty water resistant even in wet snowstorms; the exception is the leather palm, which doesn't feature a waterproof membrane backing. The leather on the palm is mostly water resistant at first; however, after a half season of use on wet storm days, the leather absorbed more water than we liked and we would need to re-treat it. This pitfall is elevated some by a unique feature: the removable inner liner on the Mercury sports a waterproof fabric outer shell. This helped keep our hands drier and kept us from feeling as cold from the potentially wet leather palms.
After our tests, we found we liked wearing the Mercury on more occasions than the Hestra Army Leather Heli Ski Mitts, as they offered higher performance. Neither the Hestra's shell nor their leather palms were as water resistant, and they would wet out more quickly and with seemingly less use. For most resort-bound skiers and snowboarders who are going to use these mittens in colder conditions, water resistance issues are less critical because the Mercury deals with drier, colder snow fantastically. We think the Mercury is a decent, but not perfect, option for closer to freezing Pacific Northwest conditions, as long as users are willing to treat the Mercury's leather palm a few times every season, because despite the BDry fabric on the liner, once the palm gets pretty wet, the mitten felt a little colder. For Intermountain skiers who ski in cold snow all the time, these mitts will crush.
All aspects of the Mercury Mitt's outer shell are bomber, featuring a durable and high-quality yet supple goatskin leather palm that is sewn with strong Kevlar stitching. The liner is average in toughness as far as its liner's tear resistance goes, but we did find that the PrimaLoft packed out a little quicker than some of the other models we tested. We also noticed a slight decline in warmth after a season and a half of medium to heavy use.
The Mercury Mitt has an above average amount of extra features which make this mitten easy to use. It features an easy to remove and quick drying liner that uses a ring of Velcro around the wrist of the liner to lock it into place. There is also a small loop on the top of the mitt to facilitate hanging the mitten open side down to help speed up drying; it will also keep snow out if you clip it to your harness for ice climbing or mountaineering. This pair of ski gloves features a wrist webbing cinch strap and a gauntlet cinch strap to help keep the snow out and the heat in. Another high scoring contender is the Capstone for its full-on feature set and heating system.
One of the unique features of the Mercury is its optional index finger slot in the inner liner of the mitt, using this slot does slightly increase "feel" and dexterity, but we like that you can also keep all 4 of your finger together to maximize warmth. Like many other mitts we tested, the Mercury features a softer fabric on the back of the thumb to make cleaning goggles and wiping noses more effective.
This award winner excels in cold weather resort riding. It's perfect for users who get cold hands easily or as a belay glove while ice climbing or ski touring. It's an okay option for wet conditions, but you need to treat the leather palm from time to time to help keep it fully water resistant.
At $110, the Black Diamond Mercury Mitt is a much better deal than either of Hestra's offerings, which both run around $145; the Mercury is also warmer and more water resistant.
We do think the fleece liner on the Hestra 3-finger takes longer to pack out and is therefore probably more durable. It's also more dexterous. But if you're after the warmest mitten with which you can still reasonably perform the basic tasks required of lift area skiing and snowboarding, then we think the Mercury's are it. And the price is right!