Intro:I've done a lot of research into materials lately and learned a lot. Big one is why I haven't been as satisfied with my merino as I used to be. This is largely due to moving from the Rockies to the South. I still do a lot of hunting out west but I've noticed that whitetail hunting here with higher humidity my go-to clothes aren't performing like they always did, new stuff I purchased I didn't care for at all, or on the other coin some pieces that I always liked I now love.
The reason I took the time to write this up is because I don't feel that all hunting companies (some are) are being transparent with the uses. This doesn't mean they are being deliberately deceitful but rather omitting info just to make a sale. It's also rather complicated that most people just go with the trends (that's what I did).
Here's what I've learned and please correct me if any information or is incorrect. None of this was done to say one material is better than the other but to provide information and let people decide what's best for them outside of the Instagram hype. Please also preface this that this is purely based on material properties and weights as I can't take into account all of the weaves in different textiles.
Material properties:Merino - Holds up to 33% of it's weight in water (which is still substantially better than cotton at 2,300%). The unique part of merino is that it holds it's water in the core of the fiber and the exterior stays dry. Giving it a dry to the touch feeling and reducing it's thermal conductivity (making it warmer when wet). It is also very breathable fabric, especially in lower weights. It is also much heavier than polyester and nylon.
Polyester - Lightweight synthetic and holds only .3% of it's weight in water and nylon holds 30% and hold that water on the exterior, making it dry quicker than merino and nylon.
Nylon - Lightweight durable synthetic but holds approximately the same amount of water (30%) as merino but is more thermally efficient because the water is on the exterior of the fiber (making you colder). Technically the breathability of the fiber is less but in my experience this isn't as relevant as it is a more durable fabric and can tolerate a looser weave.
Polypropylene - A lesser used clothing fiber from what I can find and holds almost no water at all. Making it have great thermal and dry the fastest of all.
Cotton - Holds an incredible amount of water, is heavy, durable and shrinks. Cotton is for dry environments and busting heavy brush, not in a base layer.
Uses:It is critical to emphasize that each application has it's own need and there really is NO perfect base layer for everyone. There is however, an ideal base layer for you in a certain condition. I've broke it down into 4 different factors: User Perspiration, Temperature, Humidity and Activity.
In my opinion this all boils down to one thing. Sweat! It is what we are asking the base layer to do and those 4 factors are what plays into the amount and the evaporation of sweat.
User Perspiration LevelBased on the material properties above you might gather that if you tend to sweat your ass off the same layer that works for your buddy that seemingly never sweats won't work for you. This is critical when selecting a base layer and to me this is the #1 factor. If you are a heavy sweater then a material that gives away moisture better (polyester or polypro) is going to be more ideal for you. You might never want a 100% merino piece and need a blend down the merino content depending on the remaining factors (temp, humidity, activity). If you sweat a lot and the merino isn't giving up the moisture, breathability goes down and sweating goes up making for a less than enjoyable hike.
If you're like me and just came back from the gym wearing a merino top just to try it out and got out with little to no perspiration then you might benefit more from merino. I'm not saying this as a brag as I'm really not in great shape, I just don't sweat. This is because the material will easily evaporate out the little sweat you do produce while keeping you warmer than polyester. In some conditions you want to hold the moisture you to get a cooling effect.
TemperatureTemperature not only affects the weight of the base layer you are using (grams per square meter or GSM) but it should affect the material selection as well. Remember everything plays into together and you are trying to get the sweat to evaporation ratio right.
If it's a hot and dry climate a lightweight breathable merino can actually give a cooling effect as it absorbs the moisture and releases it slowly.
HumidityHumidity is a big factor in how quickly water will evaporate. In a high temperature high humidity condition you are going to perspire a lot and not give it up. Reducing breathability and in turn making you perspire more. Merino is a poor choice in this application.
In a low humidity condition like the desert or Rockies you will burn off sweat quickly. So a higher content merino piece is more logical in this application.
ActivityThis is simple. If you have high activity you will perspire more. More active you are then the more you will benefit from a merino blend (if you don't sweat much) or synthetic (if you sweat a lot).
One thing that has been bothering me is the amount of whitetail hunters that have been buying backpack hunting gear. This isn't to knock whitetail hunters but I truly believe that the application is completely different. Hiking 3 miles in the dark to sit on a windy glassing nob overlooking a snowy expanse is different that hiking in a half mile and sitting in a stand when it's freezing out. It's both hard conditions but you need different stuff. There are pieces that overlap but that shiny loud puffy you love on the mountain is terrible for a stand. Rant over... back to base layers.
Weights:Now once you figure out what material is best for you, then you can select the weight of the material based on temperature.
- Ultralight (150 gsm minus)
- Light (145 - 175 gsm)
- Medium (175 - 210 gsm)
- Heavy Weight (210 gsm plus)