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A few years ago, I dabbled with Gumroad by releasing a free PDF booklet about vapour barrier liner (VBL) socks. This endeavor was primarily to familiarize myself with the platform's handling of PDFs. Although I also marketed my book titled 'Me, Myself & I' there, I quickly discerned that a distributed PDF could proliferate as quickly and uncontrollably as an STD in the Chamonix valley. My booklet delved into the use of VBL socks over prolonged durations, sometimes as long as 60 days, in chilly landscapes like Antarctica, Greenland, and Alaska. It also shed light on their shorter-term utility on climbs in regions like the Alps, Norway, and Patagonia.

Recently, due to some professional engagements, I revisited my booklet on VBL socks. As often happens with technical pieces, while certain sections still resonated, others necessitated a revision. My viewpoint had been profoundly shaped by nearly two months of donning VBL socks during a winter Denali climb attempt. Such a rigorous ascent required inventive strategies, especially when grappling with temperatures plummeting to -50C. In such severe conditions, one quickly discerns the gear that stands the test versus the ones that falter. Given this newfound knowledge, I felt compelled to revisit and update my insights on the topic. So, here's a refreshed and more nuanced exploration into the occasionally pungent universe of VBL socks.

Vapour barrier liner socks, or VBL socks (often abbreviated to VBL), are frequently pigeonholed as an esoteric method adopted solely by those undertaking the most challenging escapades, mainly individuals navigating the Arctic or Antarctic. Nonetheless, VBL socks can offer tangible benefits to anyone braving sub-zero temperatures over extended periods, particularly on multi-day expeditions. The colder and lengthier the trip, the more pivotal their role becomes.

A quick visit to Wikipedia will tell you that each foot boasts around 250,000 sweat glands, capable of producing up to half a pint of moisture daily. But what's the reason for our feet sweating so much? The evolutionary and scientific explanations, like many aspects of evolutionary science, are largely speculative. Most theories address sweating as a whole, suggesting it evolved to allow humans an edge in thermoregulation during pursuits, especially when compared to animals that couldn't sweat as effectively (consider how animals are often covered in fur, while humans can either have minimal hair or shed clothing). But why specifically the feet? From a climber's perspective, I'd hypothesize that well-hydrated skin on the feet is less prone to ripping or tearing. This might also explain why older individuals, whose skin moisture levels decline with age, experience more skin damage compared to the younger population.

Your feet will sweat in flip flops or Crocs, and if you're inclined to wear socks with your Crocs, you'll notice they become damp. Transition to a pair of running shoes made of nylon, synthetic leather, and closed cell materials, and your feet will perspire even more, resulting in even damper socks. Now, imagine running up a mountain with an added pair of thick socks, replacing your running shoes with heavy, non-breathable boots; your socks will be thoroughly soaked.

While wet socks in warm boots might not pose an issue for short outings, they can become problematic during inconsistent activity or prolonged stops, like spending a night just below Everest's summit or pulling on damp socks at the beginning of a summit day. Over time, these seemingly minor inconveniences can escalate into life-altering, or even life-threatening situations.

On extended multi-day excursions, socks not only become wet but also dirty. Even fully dried socks with salt-encrusted fibers will exhibit reduced insulation and moisture-wicking capabilities. For alpine climbers, the art of rotating and drying socks during long climbs is paramount. In fact, many modern frostbite tragedies can be traced back to inadequate sock maintenance. VBL socks provide a solution for nights when proper sock care is infeasible, when changing socks isn't possible, or in situations where you're compelled to sleep with boots on (advisably avoided, but sometimes it's a choice between that and facing severe consequences without them).

There's also a growing trend in using technical footwear that absorbs sweat, such as vapor-permeable lightweight leather boots versus vapor-impermeable EVA foam-lined plastic boots, wool-lined work boots, or even lightweight running or cycling shoes.

While many of these issues can often be addressed with sheer determination, enduring the pain, or by using a drying room and some newspaper, they become more concerning in extremely low temperatures or over extended durations. In such cases, solutions become essential.

Although electric socks might seem like the ultimate answer, they're limited by battery life (and once they're depleted, your toes might be at risk). Alternatively, wearing boots designed for -50-degree conditions in -20-degree weather can be overkill. In these scenarios, VBL socks offer a genuine and effective solution.

Just as a condom serves as an impermeable barrier between two active, perspiring humans, a VBL sock acts similarly between an active, sweating foot and its surrounding sock. The purpose is straightforward: they prevent sweat from dampening the sock. As a result, one could wear the same pair of socks for days or even months without the need to dry or clean them. This cleanliness and absence of moisture ensure that the socks retain their loft for as long as the VBL is intact, and internal and external moisture is effectively repelled.

For those donning leather or wool-lined boots, VB socks become an even more crucial asset. They not only prevent sweat from reaching the socks, thereby preserving their insulating properties, but they also inhibit moisture from permeating the insulation of the boots. This is particularly beneficial as such boots often struggle to maintain their insulation over extended periods without adequate drying.

When you trap all the sweat inside a sock, you might imagine that it would accumulate continuously until the sock is saturated. In reality, when you achieve 100% humidity inside the sock, your feet stop sweating. This might be a result of some evolutionary adaptation, possibly related to aquatic environments. I've worn a pair of socks for over thirty-six hours, and when I removed them, my skin felt just as damp as if I'd worn them for only an hour.

The consistent insulation in your socks means that the fluctuating pattern of "warm-wet, cold-wet" that typically occurs throughout a day becomes more stable. Your feet might feel hot when you're active but won't drop below a comfortable temperature when you rest, provided your boots can fend off the cold. However, if your boots are even slightly cold, damp socks will rapidly draw in that chill. That's why a climber wearing leather winter boots and VBL socks might have warmer feet at 1 am at the last belay than another climber in high-altitude plastic boots with damp socks.

VBL (Vapor Barrier Liner) socks are crafted from a variety of vapor-impermeable materials, ranging from plastic bags to PU-coated nylon and neoprene. If you can't draw air through it, then it's suitable for the purpose.

Commercial versions made by companies like RBH Designs, PHD, Exped, and Integral Designs typically use a lightweight proofed nylon. They feature taped seams and a drawcord at the top, ensuring the material is thin enough that it isn't felt beneath the sock. These socks come in various sizes: usually small, medium, large, and extra-large. Due to their lightweight nature, their lifespan is limited before they require repairs or replacements.

Surprisingly, the most popular VBL socks are humble plastic shopping bags. Using the ultra-thin plastic bags from checkouts (as opposed to the heavy-duty ones) offers a disposable solution that can last about a week. This is often preferable to nylon versions, as the inside can accumulate dead skin and other debris. The thinness of these plastic bags ensures that seams aren't problematic, and even if they bunch up slightly, they're unlikely to cause blisters.

If a sock does develop a leak, the amount of moisture entering the sock remains minimal. Leaks usually appear around toenails (so it's essential to keep your nails trimmed), which aren't the primary sweat-producing areas; that distinction belongs to the soles of your feet.

Are VBL (Vapor Barrier Liner) socks as comfortable as wearing a cozy pair of wool socks directly against your skin? Not exactly. They might feel a bit peculiar initially, but even though they can feel somewhat unpleasant, they're infinitely better than the sensation of frozen feet. The comfort level is significantly influenced by the type of liner socks you choose to wear (or choose not to wear), their cleanliness, and the condition of your feet.

There are two primary methods for wearing a VBL (Vapor Barrier Liner) sock: directly against the skin or over a liner or buffer.

The primary advantage of wearing the socks directly against your skin is the elimination of the need for liner socks. For prolonged use, these liners should ideally be replaced daily and washed, as they can quickly become malodorous due to the buildup of sweat and ammonia. Without these liners, it's essential for users to clean their feet thoroughly each time they remove the VBL.

Using a liner sock can mitigate the discomfort of having a sweaty plastic layer against your skin. However, the type of liner sock used is crucial for maximizing the performance of the VBL. The ideal liner should be thin yet durable, made of materials such as merino wool, polypropylene, bamboo, or Coolmax. Remember, the insulation primarily comes from the sock worn over the VBL and from your boots, with the warmth generated by your feet. A significant drawback of liner socks is the need to dry them out nightly. The only effective method for this often involves placing them against the skin, potentially intensifying any odors on your clothing.

An unconventional liner approach, which may offer the most durable and warmest combination, involves wearing a very thin synthetic fill sock beneath your VBL. Ideally, this should be made from Climbshield, as other thin insulators often lack the necessary durability. Sandwiching an insulator between two layers of quick-drying nylon allows these socks to dry more rapidly than standard liners. The Wiggy’s Lamilite sock (where Lamilite is essentially Climbshield) is the only product I've found that meets these specifications (Rab Hotsocks might work, or you could just make your own using Climshield and Pertex).

It's a given that you should maintain your toenails, ensuring they're trimmed short and free from any sharp edges that could damage the socks. I'd also recommend spending a few weeks exfoliating away dead skin before a significant trip. Wearing VB socks can be likened to undergoing an intensive foot spa treatment, with considerable dead skin shedding daily. Wear VB socks consistently, and in a few weeks, your feet will appear rejuvenated!

After wearing the VB socks throughout the day, remove them and turn them inside out. This allows the sweat to freeze, making it easier to shake off later. Clean your feet with snow or water, allowing them to dry thoroughly. Then apply anti-fungal powder, which helps further dry the feet, leaves them smelling fresh, and prevents fungal infections.

Once you've done this, you can don a pair of warm 'night socks' or simply put your wool socks back on for sleeping (resting won't dampen the socks). In the morning, slip on your VB socks, and you're ready to go.

Neglecting foot care in this manner can lead to problems in just a few days. The issue won't be limited to minor athlete's foot symptoms; you could develop severe open sores between your toes. Remember, much like how even the tiniest cuts in the jungle can fester and become debilitating, the interior of a VBL creates a similar microclimate, making it a potential breeding ground for infections.

As I mentioned in my introduction, the duration of your outdoor activity, combined with the importance of retaining the loftiness in your socks, determines how essential it is to use a VB sock. If your boots are extremely warm or the weather isn't very cold, having wet socks isn't a major issue. However, if you end up with wet socks and let them remain damp in your sleeping bag, only to later insert them into frozen leather boots the next day, you could face challenges. Conversely, if you're planning a 100-day ski trip to the South Pole and back, wearing soft boots and carrying only two pairs of socks, VB socks become indispensable. This principle also holds true for high-altitude mountain expeditions like those to Denali, Ama Dablam, or even Mont Blanc. VB socks prove especially beneficial when paired with leather boots since socks play a significant role in warmth retention. Ensuring they stay dry not only enhances your safety – as cold and frozen feet can be distracting and potentially hazardous – but also elevates your overall comfort and well-being during the journey.

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