Arc’teryx Phase AR Baselayer Review

Arc’teryx Phase AR Baselayer Review
Phase AR in action in WA
Review by Claire Giordano

Born and raised in the Pacific Northwest, there are two items I will never have too many of; baselayers and fleece jackets. A good baselayer top is the foundation of an effective layering system ready to meet changeable weather conditions from coastal rains to snowy peaks. Because we take our baselayers so many places, we demand a lot from them. We expect them to be warm but not too hot, durable and yet lightweight, and cozy but not overly bulky.

Over the last five months I got to adventure with the new Arc’teryx Phase AR baselayer, and it is now my top-pick for a synthetic shirt.


Baselayers, like any piece of outdoor gear, have a few basic variations. First, they are usually made from either wool or a synthetic fiber like polyester. Wool has been around for a very long time and has come a long way from the boiled itchy layers our grandparents used. Most modern wool layers are made from Merino wool, which is soft and not itchy to most people. Wool is known for its lack of odor but does take longer to dry than modern synthetic counterparts. Synthetic shirts are also incredibly lightweight and provide excellent UV protection. Synthetic and wool are both great options, and I like having a variety to bring on trips.

When I put on the Phase AR at the start of a five day backpacking trip, the first thing I noticed was the fit. It is a true next to skin baselayer; not too tight but form fitting enough to effectively wick moisture away from my skin. For the new Phase AR, Arc’teryx redesigned the fit, and I like it a lot. It retains the zoned materials (lighter under the arms) but got rid of the rather silly looking grey for the lightweight panels and replaced it with matching color. The seam lines are also very flattering, making this the most sleek looking baselayer I own. The zip neck goes to the perfect height where it adds a little extra warmth without irritating my chin or rising annoyingly high on my face. The zip also goes down far enough on my chest to provide needed ventilation. The fabric also has a nice feel to it and is durable. Many of my other synthetics pill at the hip belt buckle after a few trips, but the Phase is still holding up great in this area. It also withstood bushwhacking and rock scrambling without snagging.

The Phase AR in action at Mount Rainier National Park. Picture by Grace Giordano
The Phase AR in action at Mount Rainier National Park. Picture by Grace Giordano

It is worth noting that the layer does have a seam across the top of the shoulder, but it did not cause an issue (these seams, if done improperly, can be a big annoyance and cause of chaffing). Fortunately these are flat enough I do not notice them at all, even under a fully loaded backpack.

Performance wise, I think the shirt dries a little faster than my other synthetics. When my older synthetics get wet they can feel clammy. This shirt, however, felt decently dry to the touch even when I stopped for a longer break after a sweaty and steep scramble. The garment is made from Arc’teryx’s Phasic AR fabric which uses different polyester yarn structures on the inside and outside, which is likely why it dries so nicely. I was glad for the quick dry time every evening when I could put the shirt out on a line for a few hours and get it mostly dry, even while camped in a damp lake basin. Bringing it in the tent at night dried it the rest of the way. My wool baselayer took longer to dry out in these conditions.

Even in full sun, the Phase AR regulated temperature well.
Even in full sun, the Phase AR regulated temperature well.

During the backpacking trip, I don’t think I ever took this off once I left camp each day. I was thoroughly impressed by its temperature regulation. From sunny scrambles on scree to rambling in windy ridgelines the shirt did great. It was also the perfect layer under my windbreaker, wicking moisture off of me to prevent the dreaded clammy jacket. I usually praise wool for its thermal regulatory ability, but I think the Phase AR is just as good as my favorite wool top.

Now, the question we all wonder about; the sink factor. The stink of synthetic shirts is why I now gravitate toward wool on most trips. By the end of my five day trip this shirt was definitely funky, but not as bad as I had feared. It wasn’t until the second day that I noticed a little smell, which is a big improvement over some of my other layers that are annoying hours into the first day. In this respect, the Phase AR is at the top of its class, with only the new treated Patagonia Capilene giving similar performance for me (I will note that under the Phase AR I was wearing a very lightweight wool t-shirt, which helps with the stink but won’t fix it).

Final verdict: Quick drying, great looks, good temperature regulation, and very comfortable. On days I want a synthetic shirt this is the one I grab. It its also so flattering I have been wearing it around town with a fluffy scarf most of the winter.

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