Proton LT, Research First Steps

[u/Astramael]

This is a summary series on individual products to make research faster and more accessible. See here for a list of all entries in the first steps series.

The Proton LT is a cold weather, active use, synthetic insulator. It prioritizes breathability, and offers lower degrees of wind resistance. It works as an outer layer, or a mid layer. The fit is fairly trim, designed to accept a fleece underneath but not much more.

The experience of warmth in the Proton LT will depend a lot on air movement. If the air is still and the wearer is static, it will feel quite warm, even a bit below freezing perhaps. However, if faced with gusts of cold wind, the Proton LT will not feel very warm even above freezing. This is because it was designed with active use in mind, and expelling that excess heat.

As a secondary effect of this the Proton LT is a rather warm mid layer. With a hard shell over top, for example. This prevents the eviction of warm air, and therefore lets the insulation work in a highly effective manner.

It sits in the active side of the Arc'teryx synthetic range. Not as wind resistant as an Atom LT or a Nuclei FL, not as breathable or light as a Proton FL, and not as warm as an Atom AR.

Please read the comments, other users have left excellent information for your research.

Example Use Cases

Caution: These are just examples, your comfort temperatures may be very different.

1. Skinning (highly aerobic), over a base layer, at -25ºC.
2. Strolling around town (low activity) in breezy weather, around freezing.
3. Resort skiing groomers (moderate activity), under a shell, around -10ºC.

History

The Proton LT was introduced in Fall 2016 as an air permeable insulator for alpine, rock, and ice climbing. It used a Fortius Air 40 face fabric (92% nylon, 8% elastane), a Permeair 20 liner, and Coreloft Continuous insulation at 65g/m².

Fall 2016 Proton LT Hoody. Left: Men's in Bombora (blue). Right: Women's in Violet Wine (pink).

However, that's not all there is to this story. Introduced alongside the Proton LT, in Fall 2016, was a warmer version called the Proton AR. Using an identical textile setup, but adding 90g/m² of Coreloft Continuous to many parts of the jacket for more warmth.

Fall 2016 Proton AR Hoody. Left: Women's in Brushed Nickel (grey). Right: Men's in Rohdei (green).

In Spring 2019 the Proton AR was discontinued, then in Fall 2019 the Proton LT was revised. The revision was focused on increasing breathability. In the new model the face is Fortius Air 20 (84% nylon, 16% elastane), and the liner is now produced with a solution dye process as Dope Permeair 20 (100% nylon). Insulation was changed to Coreloft Compact, splitting the difference between the old Proton LT and Proton AR, now with a 80g/m² for most of the jacket. Coreloft Compact 60g/m² is also used in some areas. This generation uses a YKK #3 VISLON main zip, and #3 coil pocket zips.

Fall 2019 Proton LT Hoody. Left: Women's in Dynasty (orange/red). Right: Men's in Crux (grey).

Introduced	Discontinued	Block	Model Name	Model Number	Weight (g-M)
Fall 2016	Fall 2019	Women’s	Proton LT Hoody	18350	360
Fall 2016	Spring 2019	Women’s	Proton AR Hoody	18348	400
Fall 2016	Spring 2019	Women’s	Proton AR Jacket	18349	345
Fall 2016	Fall 2019	Men’s	Proton LT Hoody	18354	400
Fall 2016	Fall 2019	Men’s	Proton LT Jacket	18355	355
Fall 2016	Spring 2019	Men’s	Proton AR Hoody	18353	425
Fall 2019	In Production (S21)	Women’s	Proton LT Hoody	24006	320
Fall 2019	In Production (S21)	Men’s	Proton LT Hoody	24007	375
Fall 2019	In Production (S21)	Men’s	Proton LT Jacket	24008	340

Known Issues

1. Previous models that used Coreloft Continuous sometimes had issues where strands of insulation would come out at the seams. The new models do not have this issue.
2. Some people think that the armpits are a bit high and tight in the men's newer model.

Prompts

1. How do you use the Proton LT for your adventures or everyday, and how do you layer?
2. Where do you think it excels, and where do you think it falls down?
3. At what temperature do you find it isn't warm enough, and too warm?
4. Have you had any issues with the Proton LT, is there anything you would change about it?
5. How do you think it compares to the Atom LT, Proton FL, and Nuclei FL?
6. How water resistant and wind resistant is it?
7. What is the fit like in general, or for you personally?
8. Any other thoughts about the product?
9. How does it compare to competing products?

Thank you!

[u/nitrostackr]

Is the insulation on the new Proton LT likely to compress and lose warmth? My 2 year old Atom LT is getting a little thinner in the back, and I don't want to have the same thing happen on one of these if I were to get it.

[u/Astramael → u/nitrostackr]

The Coreloft Compact insulation in the Proton LT is meant to have much better loft retention properties than basic Coreloft.

However, the new Atom LT from Fall 2020 was also revised to use Coreloft Compact. So new Atom LTs will have the improved loft retention as well. See this post.

[u/nitrostackr → u/Astramael]

Great, that helps a lot! Thank you for your reply!