Arc'teryx Thorium AR

The Arc’teryx Thorium Hoody and Thorium Jacket, in both men’s and women’s versions, are down jackets best suited for use in dry, cold conditions. All models of the Thorium are lightweight, packable and incredibly comfortable. And thanks to an update that started with the 2023 models (and remains for the 2024-2025 versions), they feature slightly more goose down insulation, two-way zippers, and a looser fit, among other tweaks we’ll detail below. 

Bottom line: The Thorium Hoody and Thorium Jacket are excellent standalone cold-weather down jackets for casual wear in primarily dry weather. They’re also quite a bit warmer and heavier than their Arc’teryx Cerium counterparts. Because they lack the waterproof and windproof Gore-Tex outer found on some other Arc’teryx down-insulated jackets like the Therme Parka and Beta Insulated Down Jacket, the Thorium is not suited for wet conditions. For insulated midlayers and outerlayers to be worn during high-output activities, we recommend synthetic insulated pieces like the iconic Arc’teryx Atom or the Arc’teryx Proton.

Note that the Thorium Hoody and Thorium Jacket were previously called the Thorium AR Hoody and Thorium AR Jacket. While there were some changes to each model, the core product remains largely the same.  

Arc'teryx has a handy jacket-finder tool to match your specific needs and uses: https://arcteryx.com/us/en/shop/jacket-finder 

Here's how Arc'teryx compares the men’s Thorium Jacket vs Thorium Hoody: https://arcteryx.com/us/en/compare/X000007380/X000007250

Warmth

On the whole, the Thorium line of jackets is fairly warm, especially considering the relatively light weight of each piece. This shouldn’t come as a surprise given the incredible warmth-to-weight ratio of down insulation. All versions of the Thorium - hoody, jacket, parka and vest - are insulated with 750 fill power European grey goose down certified by the Responsible Down Standard (RDS). Arc’teryx tends to use goose down instead of duck down because of its higher fill power (which also makes it more expensive).  

As with other down-insulated Arc’teryx jackets, the Thorium features “Down Composite Mapping,” which Arc’teryx describes as the strategic placement of synthetic insulation in moisture-prone areas. In the case of the Thorium, synthetic Coreloft insulation is used in areas like the cuffs, hood, zipper guard, shoulders, chest pocket and mid-sleeves. The Thorium Hoody, Thorium Jacket, Thorium Parka and Thorium Vest all use both Coreloft 140 and Coreloft 80. 

To that end, the Thorium performs very well as a standalone outer layer in cold weather. In fact, it's Arc'teryx's warmest traditional down jacket (traditional in the sense of having a nylon face fabric like most puffers). It kept us warm throughout an extended trip to Iceland in March, and it's a go-to piece whenever the thermometer dips below 40 degrees. 

A word about down and synthetic insulation

Down is a fantastic insulator when it’s dry because it works by trapping air within its vacant spaces. Conversely, down clumps together when wet, which means those air pockets disappear and lose all their insulating power. That’s why down jackets, especially those like the Thorium that lack a waterproof outer fabric, are great for cold, dry conditions but not good for wet conditions or during activities in which the user produces a lot of their own moisture (i.e., sweat). 

Synthetic insulation like Coreloft, on the other hand, doesn’t lose its insulating power when wet. To better understand fill power, the difference between down and synthetic insulation like Coreloft, and how all of it affects the warmth of a jacket, check out our detailed explanation here.  

One other note about warmth: Fill power speaks to the insulating quality of the particular type of down used. Higher fill power means more pockets of air in which to trap heat and provide warmth. Most quality outdoor brands use down with fill power between 650 and 850. But fill weight is also very important in determining the warmth of a down jacket. Fill weight is the total amount of down used in a jacket. In the case of the Thorium Hoody, the men’s size medium has 147 grams of down. That compares to 113 grams of 850 fill power down in the size medium men’s Cerium Hoody. Even though the Cerium uses a higher fill power down, the significantly greater fill weight of the Thorium's 750 fp down means it is a warmer jacket. (By the way, we compare the Thorium and Cerium here: https://outdoorcrunch.com/cerium-vs-thorium/. 

We know warmth is fairly subjective, but to help provide a baseline for what to expect from a jacket, we’ve compiled jacket temperature ratings based on our extensive research on fill power, fill weight and synthetic insulation CLO values. Check out the chart below: 

Weather resistance

The point of reinforcing a down jacket with synthetic insulators like Coreloft is to provide at least a little bit of weather resistance. Because no matter where you live, you don't want to be completely vulnerable to unexpected weather changes. Zero protection against precipitation is usually unacceptable to most of us.

In addition to the strategic use of Coreloft, all models of the Thorim use an Arato 30-denier nylon face fabric that is treated with a FC0-DWR (durable water repellent) finish. DWR finishes are sprayed onto the surface of jackets as a final coat - think of it like a wax on your freshly cleaned car. DWR coatings absolutely help jackets repel some precipitation, but they are not miracle workers. Extended exposure to steady precipitation will eventually leave your Thorium soaked and relatively useless from a warmth standpoint. Pack a waterproof shell if you expect to to encounter serious moisture.

We put the Thorium Hoody to the test during a recent trip to Iceland, where we experienced all manner of precipitation - snow, rain and drizzle (welcome to Iceland in March). The Thorium did a good job in terms of withstanding the moisture for, say, up to half an hour at a time. 

If you need a weatherproof jacket with at least the same amount of warmth, then consider down jackets with Gore-Tex outers like the Beta Down Insulated Jacket, the Therme Parka, or synthetic-insulated options like the Nuclei SV (Men's) and Atom Heavyweight (Men's - Women's - read our review). 

In terms of wind resistance, the Thorium and its Arato 30 nylon face fabric is a solid but not perfect option. It’s certainly wind resistant, but it’s absolutely not windproof. Again, if you need windproof protection, check out options like the Nuclei (Men's - Women's - read our review). 

Breathability

While down is not a very breathable insulator, Arc’teryx has done something with the Thorium it hadn’t previously done with any of its lightweight down jackets: it added a two-way front zipper. Why does it matter? Because having the ability to keep the upper half of your Thorium zipped but the bottom half unzipped at least gives you some control over temperature. And on longer jackets like the Thorium Parka, being able to unzip the bottom portion makes sitting way more comfortable. For climbers, the two-way zipper also allows easy access to a harness while staying warm.

There are a couple downsides to two-way zippers. For one, they tend to break easier and more often. They also take a bit more time and effort to zip and unzip compared to traditional one-way zippers (especially when wearing gloves). But we’ll take the breathability and comfort advantages any day. 

Packability

We’re fans of insulated jackets that stuff into themselves. Another advantage of down is its compressibility, which is great when you’re looking to cram a reliably warm layer into a backpack, suitcase, etc. The Thorium passes the test, with all models except the women’s XLong Parka coming with stuff sacks.  

Oh: Stuffing and unstuffing a jacket over and over and over again can take a toll on down’s loft and therefore its long-term insulating power. Don’t store your Thorium Jacket or Hoody in a stuff sack for extended periods of time. The ideal way to store them - and any down garment or sleeping bag for that matter - is by hanging them. 

Arc'teryx Thorium Hoody, Jacket and Parka: Similarities and differences among the models

We previously mentioned some of the updates that occurred to the Thorium line for winter 2023 - updates that remain with the 2024 versions. Those changes include:

• Two-way main zippers added to all versions except the women’s Thorium Jacket and the women’s Thorium Vest 
• Zippered external chest pocket added to the men’s Thorium Hoody and Thorium Jacket, and the women’s Thorium XLong Parka
• The fit is now more comfortable (i.e., looser) through the chest, waist, hip and thigh (for parkas). This revised fit also makes it easier for layering clothes under your Thorium.
• The down baffles are a bit larger 
• The insulated StormHood is helmet compatible and adjustable
• The amount of 750 fill power down increased slightly

There also were subtle changes in the weight (slight increase) and center back length (slight decrease). Check out our jackets database table below for more details. 

Helpful links:

• Arc'teryx's comparison of men's Thorium Hoody to Thorium Jacket: https://arcteryx.com/us/en/compare/X000007380/X000007250
• Arc'teryx's comparison of all four women's Thorium models: https://arcteryx.com/us/en/compare/X000005659/X000005965/X000008531/X000005993

Additional Arc'teryx Thorium features

Pockets

All Thorium models in both men’s and women’s versions come with two zippered handwarmer pockets, but only the men's versions are lined with micro fleece. The men’s Thorium Hoody and Thorium Jacket as well as the women’s Thorium XLong Parka also get a zippered external chest pocket and two internal dump pockets. The women’s Thorium Hoody and Thorium Jacket, get only a single internal dump pocket 

StormHood

The men’s and women’s Thorium Hoody, the women's Thorium Jacket (curiously), and the women’s Thorium XLong Parka come with an insulated StormHood, Arc’teryx’s adjustable, low-profile, helmet-compatible hood. The hoods are adjustable via a single pull adjuster at the rear of the hood. For more about StormHood (and how it compares to Arc’teryx’s increasingly rare DropHood, check out our article about them).

Cuffs

All Thorium models except the women’s Thorium XLong Parka feature stretchy cuffs. The parka’s cuffs have internal gaskets to maximize warmth. 

Hem adjusters

All Thorium models except the women’s Thorium XLong Parka come with dual lower hem adjusters for cinching the bottom of the jacket for heat retention, fit, and to keep out those nasty wind gusts. 

How to wash and care for your Arc'teryx Thorium (and other down jackets)

Down is such an incredible insulator because of the tiny pockets of air within it that trap your body's heat and thus keep you warm. But when down becomes wet it loses its insulating power and is essentially worthless. It also takes a long time to dry. All of this is to say that caring for your down garment is essential to keeping you warm and to making sure that expensive jacket performs for years and years. 

There's no need to wash your down garment until you know or see that it's dirty, and that's because things like dirt and sweat compromise the ability of your jacket's high-end fabrics to repel moisture. And like we said, moisture is bad for down. 

When it is time to wash your down jacket, here's what Arc'teryx recommend:

1. Close the main zippers but leave open pocket zippers (and make sure all those pockets are empty

2. Release the tension on any drawcords, like the one for your StormHood

3. Loosen and secure any Velcro cuffs 

4. If you have a top-loading washing machine with an agitator, toss your garment in a mesh bag to help protect it

5. Use a mild detergent without scents, dyes or fabric softener, and wash on medium heat with a permanent press or gentle setting. Add an extra rinse cycle to ensure all the detergent is washed out. This down detergent from Nu is recommended and sold by Arc'teryx.

6. If you need to refresh your jacket's DWR (durable water repellent) finish, this is the time to do it. Close all zipper, hang up your damp garment, and spray the DWR evenly and thoroughly across the outside of the coat. Arc'terx recommends this Nu Durable Water Repellent spray.

7. When finished washing, turn the jacket inside out and put it in the dryer on a low heat setting. Add two clean tennis balls or other dryer balls to help the down regain its loft. Note you may want to turn the jacket inside out again to ensure all areas of the down get completely dry.

Voilà! Your down garment is hopefully as good as new.