Reviews You Can Rely On

How We Tested Base Layers

Tuesday March 29, 2022

Testing these base layers in real-world situations, as well as specific tests conducted in our lab, are what allow us to provide you with such in-depth reviews. From dragging them up chimneys on desert towers to skinning up volcanoes in the Pacific Northwest, we run these tops through the gauntlet. Below is how we test for each metric.

base layer - canyoneering in utah, the patagonia capilene air breathed well...
Canyoneering in Utah, the Patagonia Capilene Air breathed well keeping us from overheating in temps in the 60s but didn't stand up to dragging it through sandstone slots.
Credit: Roland Mott


This one is simple. We wear them in really cold conditions — alone and part of a layered system — and we see how efficient they are at keeping us warm when temperatures drop into the uncomfortable ranges.

base layer - taking a breather from the lung-bursting skin track in frigid dawn...
Taking a breather from the lung-bursting skin track in frigid dawn temps.
Credit: Adam Zagorski


We use a combination of real-life experience as well as a regulated tests within the lab for this metric. We skinned up Mt. Hood, hiked steep talus cones to climb desert towers, pedaled steep mountain biking trails, and ran winding mountain trails in Colorado. In the lab, we test each top, one at a time in a temperature-controlled, indoor environment — we work up a sweat with the same short but rigorous exercise routine, and then time how long it takes for our skin and the inside of our shirts to dry after stopping.

base layer - breathing it out up a classic front range climb before a heavy snow...
Breathing it out up a classic front range climb before a heavy snow is forecasted to start in the next few hours.
Credit: Roland Mott

Comfort & Fit

We wear them a lot, and with an extremely critical eye. We consider the comfort of the fabric of each layer next-to-skin. We compare the way they fit on testers of different body types, examine the stitching patterns and design features. We record the length of the torso and arms, judge how comfortable the collar is, comment on the stretch of the fabric, and note specific features like a drop-tail hem, tapered arms, and thumb loops. We critiqued how they form to the body, whether they bunch up when layered, and make notes on at what point they become uncomfortable during strenuous activity. If our testers find themselves wanting to wear a layer all the time, then that is a sure-fired way to know that a particular product has climbed its way to the top of our list.

base layer - coffee and oatmeal - two things you don't leave your bag before...
Coffee and oatmeal - two things you don't leave your bag before having in your hands. The Rab Merino+ 120, the perfect fit and top for crisp fall nights in the southwest. We loved the thoughtful design and fit of the Rab.
Credit: Roland Mott


This is another combination of thoughtful observation while at play, and a controlled test in the lab. We beat the heck out of these things — we drag them up desert towers, scrape through slot canyons, and bushwack through thickets.We also send them through repeated wash and dry cycles to see how well they hold up under more normal circumstances, and note what tends to breaks down fine fabrics the fastest.

base layer - putting the icebreaker 200 oasis to the test dragging it up a...
Putting the Icebreaker 200 Oasis to the test dragging it up a squeeze chimney on an obscure desert aid climb. Being 100% merino wool, we were impressed with the Oasis. Still not as durable as the synthetic Arc'teryx Phase AR but it stood up well to the abuse.
Credit: Kricket Servis

For our lab test, we take a section of the fabric at the elbow and vigorously drag it back and forth against a 1-foot piece of rough and textured sandstone to see how the fabric holds up to abrasion. This test provides us with a clear picture of what fabrics will stand up to abrasion over time — and which are designed for activities like rock climbing — and which products that are simply not built for such rigorous activites.

base layer - we enjoyed living in this top for days at a time, whose merino-blend...
We enjoyed living in this top for days at a time, whose Merino-blend helped fight off stink... but not quite as long as other full-wool competitors.
Credit: Jill Rice

Drying Speed

The time a base layer takes to dry while next-to-skin and the time it takes to dry away from the body can vary significantly. First, we note a layer's ability to dry next-to-skin through activity, working up a sweat while mountain biking, trail running, and skinning.

As a laboratory test, we completely saturate each top and lay them flat dry in the sun. This test simulates hand-washing and drying out a piece of clothing like you would on an extended backpacking trip or expedition. Conveniently, the timed results often correlate directly with a top's ability to efficiently dry on the body, and provides us with specific times to compare the products with one another.

base layer - tops during the dry speed test.
Tops during the dry speed test.
Credit: Roland Mott

Layering Ability

We incorporate each top into any and every layer combination we can imagine. We observe how they feel against the skin, and how well they layer with different clothes worn over top. We layer tight and sticky technical fleece mid-layers, wool sweaters, slick nylon down jackets, and tacky synthetic insulating layers like the Patagonia Nano Air or R1. Any combination we can think of, we try out.

base layer - a handsome layering system with the rei co-op merino as the base...
A handsome layering system with the REI Co-op Merino as the base, Patagonia R1 for a mid layer and the Outdoor Research Transcendent Down Hoody as the outer insulating layer.
Credit: Roland Mott

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