A Custom-Made Night’s Sleep | The Firewater Sleeping Bag

A Custom-Made Night’s Sleep | The Firewater Sleeping Bag

Words by Mountain Equipment

There’s more to our products than we often let on. From countless months of product research and development that often stretches into years, to honest and profound feedback on prototypes from our Pro-Team members and trusted Partners. It takes a lot of time and effort to create the kit that we’re proud enough to present you with. But that doesn’t mean we don’t like the occasional last-minute challenge.

Very occasionally, we are approached to create something that simply hasn’t been attempted before. From unique custom-made Sleeping Bag designs with specs the likes of which the world has never seen, to practical and idiosyncratic customisations of production-line classics. We thrive off these challenges, and it’s at the core of everything we do. To create the best gear in the world, under any condition.


Uisdean Hawthorn, is currently in India attempting a new route on a huge peak deep in the Karakoram. It’s an objective he’s been working towards for over a year, and one of the things he needed for this route was an extremely lightweight sleeping system. It’s not the first time he’s asked us for a custom development…

Uisdean is no stranger to weight-saving solutions on routes, and has previously had a lot of success with sharing sleeping bags during big trips: it saves weight and you can share body heat. A no-brainer when performing under extreme conditions.

Earlier this year during Spring, we made him and Tom Livingstone, one of our other Pro Team athletes, a fully-customised two-person bag. We did it all from scratch, here in Manchester: the combined efforts of our longest-serving machinist who has been making sleeping bags for almost 30 years, and our newest machinist, who – despite years of sewing expertise – was relatively new to the world of down and sleeping bags.

Making an all new block, custom patterns, and then sewing and stuffing the bag took them two full days, working round the clock so it’d be ready in time. We know how to work to a tight deadline.

With a short time-frame, the pressure was on to deliver the custom 2-person sleeping bag to Uisdean and Tom before their Alaska expedition.

The bag was a big success; despite weighing under a kilo it was warm enough for Alaska and temperatures of -35 °C. A siliconised-nylon tent groundsheet, footbox big enough for four feet, and a huge cowl which fitted over the overstuffed body were just a few of the innovations on what was a staggering sleeping bag. We don’t think there’s a warmer sleeping system out there for two people – especially when you consider that it weighs under 500 grams per person.

The brief for Uisdean’s India expedition was a little different, however; he needed a bag which he could sleep in alone as he feared that no ledges on the route would be big enough for two people to sleep on side-by-side.

Also, despite the altitude of the Karakoram, night-time temperatures in the summer are seldom extremely cold. As a result, Uisdean wanted the very lightest bag we could make, something that would be significantly warmer than having no sleeping bag at all, yet had no major weight penalty. A few discussions with him, deliberations amongst the design team, and then a bit of frantic maths suggested we could make a sleeping bag that would come in at about 310 grams.

That sounded pretty light to us.

In terms of development, it was far easier than the two-person bag: we took the Helium Solo, our lightest sleeping bag in production as a template, and then ‘Fired’ it.

The already very lightweight Helium shell and lining fabrics were replaced by the 26 g m/2 Plasma 10D fabrics from the Firefly/Firelite/Fireflash series of bags, and the premium duck down was replaced by our very best 800 fill power goose down.


Weighing in at a mere 298 grams, the Firewater Sleeping Bag is a contender for one of the lightest sleeping bags in the world.

We then removed the zip from the bag, as this shed even further weight. For Uisdean, every single gram mattered.

The finished bag weighed in at an incredible 298 grams while in its stuffsack, beating our estimated weight and leaving the bag only a few grams from the World Record, despite being a much warmer bag. Roughly the size of the 700ml whisky bottle, and twice the size of a can of beans, this custom-made sleeping bag is one of the lightest we’ve ever made.

In terms of warmth, this sleeping bag comes in a tad warmer than the Helium Solo, part of our Extreme Light range of sleeping bags, and receives a Good Night’s Sleep temperature of about 6 °C.

Uisdean will be using it in temperatures below 0 °C, but with a robust down jacket (he has a prototype Skyline Jacket with him too) and a willingness to suffer in the Greater Ranges, we hope it’ll be warm enough.

When we finally finished this super lightweight sleeping bag, we still didn’t have a name for it. But with a little help from our followers on Facebook, one name was suggested that seemed appropriate: introducing the Firewater Sleeping Bag.

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