"Thermal underwear keeps you warm!"

"Moisture-wicking fabrics keep you dry!"

These are two of many ridiculous statements that have been repeated in the echo chamber of outdoor gear brands (along with their marketing and public relations agencies), uninformed users, and so-called outdoor experts for as long as I can remember.

Here's a screenshot from Google's #1 ranked web page in the outdoor industry about base layer apparel. I want to warn you before you read it, because I don't want you to become indoctrinated with Things That Aren't True, but I also want you to read it so we can break it down later in this letter in an effort to help you become a more educated consumer of outdoor gear.

OK, go:

1. It let's the reader know that they do not have the "ultimate" layering system yet.
2. It establishes (perceived, but not true) authority by making the claims that "fabric is your most important decision" and "you need it to wick well" and "a wicking fabric has to be in direct contact with your skin to do it's job" etc.
3. There's a nice button at the bottom so that once you've read the post and convinced yourself that you just became an expert, you're ready to shop for a base layer.

Retailers, bloggers, and affiliate marketers make enormous amounts of money on these types of pages.

They write this type of copy to increase their search engine footprints and use the power of persuasion to get people to purchase what they are promoting.

It's not a deceiving practice in and of itself - just be aware of it (in fact, do you see how we are using it in this letter: we want you to learn more about this topic in the testing report and the livestream Q&A event linked at the bottom).

However, it is absolutely deceiving if what you are telling the reader is not true.

That brings us to the next part of this letter - breaking down the copy and identifying what's true, and what's not - about this post.

Let's do that by evaluating specific claims in the copy:

1. Marketing Claim #1: "Fabric is your most important decision."

No, it's not.

There is never such a a thing as "the most important thing..." or "the best..." or "the ideal..." or whatever someone else is recommending to you - the person who is shelling out the actual money to buy something.

This is classic marketing copywriting because it brings the consumer's attention to something that may not actually be important to them.

For some users, fabric is not the most important decision. The decision should also be informed by style, fit, ventilation, durability under pack straps, comfort across a wide temperature range, etc. - you get the idea. So much more goes into choosing a base layer than what can be communicated in a 300-word blog post. But if you make it 3,000 words, then that darn buy button gets scooted way down at the bottom and most buyers are too lazy to learn.

(An aside: if that's you, then I'm surprised you made it this far, but I hope you understand what I'm getting at here - I'd really like to see you become an outdoor expert who is a very capable shopper and disciplined about what you buy. So keep going!)

The funny thing about this statement, is that while there are salient differences between natural and synthetic fibers, for some types of natural fiber fabrics vs. some types of synthetic fiber fabrics:

There is no perceptible difference in thermal performance or moisture-wicking performance!

You see, it's more sophisticated than a sound bite, isn't it?

2. Marketing Claim #2: "...you need it to wick well."

No, you don't.

Wicking is NOT the holy grail of real or perceived clothing comfort. If wicking proceeds too quickly into a fabric with an extraordinarily high surface area, you'll experience such an rapid rate of evaporative cooling when your output decreases that too much heat can be sapped from your body.

Likewise, in warmer conditions, having some moisture against the skin will promote both evaporative and conductive cooling that can keep your core temperature low so you stay comfortable.

So, you don't need the fabric to wick well:

You need the fabric to wick appropriately for the layering system and conditions you are experiencing.

A lot of this depends on the skill you have at regulating output, and what types of layers (and how you're adjusting them) are worn on top of your base layer.

3. Marketing Claim #3: "...thicker fabrics = more warmth."

This is true only when looking at the exact same types of fibers, yarns, weaves (or knits) and just comparing differences in their average thickness.

But that's not a useful determinant of how garment warmth compares to each other between brands, or even between different product lines made by the same brand.

Warmth is a function of fiber type, fabric weave (or knit) type, fabric weave (or knit) density, fabric weave (or knit) 3-D structure (and thickness), how much moisture is absorbed onto and into the fibers and the interstices of the fabrics created by the weave, and the ability of the fabric (and fit) to entrap air pockets that are resistant to convective movement.

4. Marketing Claim #4: "A wicking fabric has to be in direct contact with your skin."
 

1. How does wicking work?
2. Are brands deceiving to us about how effective their products wick?

In this article, Backpacking Light contributor Stephen Seeber not only gives us a comprehensive primer on how wicking works, but introduces us to test methods and scientific data that evaluates manufacturer claims of wicking performance.

In addition, wicking and base layers will be the topic of our next livestream event and Member Q&A, so mark your calendars for January 27. More info:
 

• Base Layers, Wicking, and Backpacking (Livestream) - January 27, 2022 6 PM US Mountain Time

As with all of our Member Q&As, the event will be recorded and the recording made available to Members.

Thank you for your time today - and for being an email newsletter subscriber. I hope we lived our values (advocacy, expertise, and generosity) and that we provided you with access to trusted expertise so you can hike more confidently.

Become a member today and help us rehabilitate the commercially-driven outdoor experience, because it belongs to us - the hikers and other outdoor recreationists that find peace, solace, and healing in nature.

Happy Trails,
Ryan Jordan
owner/founder/publisher