Base Layers and the Differences- Part 1, by A.S.

Today there is a great deal of knowledge on the Internet and outdoor magazines about “layering”, so most people who are daily or frequent readers of SurvivalBlog would have a good understanding of using different layers to keep the human body neither too cold nor too hot. Either one will have life threatening consequences if not managed correctly away from urban areas. For the purpose of this article my intention is to explain, in layman’s terms, some of the finer points of using different base layer fibers and their properties, as well bring to attention a new space age fiber, namely Tencel, that utilizes the latest in technology. (There will be more on Tencel later.) Today, base layers come mostly in three different materials– wool/Merino, polypropylene, and cotton. (I steer away from cotton.), Sometimes manufacturers use mixes of two materials such as Merino and poly.

My experience in discussing this subject by the way is through my involvement over about 35 years in mountain rescue and bush survival. I am by no means an expert, but I have long time field use of what works and what does not. That being said, I will also explain what I use and why I use it for serious outdoor use. Of course this use applies to long-term SHTF use! So, let’s get started.

1. Polypropylene

The most common and inexpensive material is polypropylene, which is a by-product of the petroleum industry, and as such polypropylene sheet is manufactured from a propylene monomer (strands bonded with elastomer), using a relatively safe gas for the process. This in turn is a waste by-product that used to be burned off into the atmosphere, contributing to greenhouse gas emissions. Now the end product is used for clothing, and by far the biggest type of clothing where it is used is for thermal base layers. It is also used for cheap, dollar store clothing as a consequence. The more polypropylene used in products the more better help in reducing greenhouse gas emissions. As far as using the material for base layers, polypropylene is spun into fibers and then woven by machine onto a loom and then cut, dyed, and stitched. The benefits of using polypropylene as your base layer or next to skin layer is that the material, when wet, dries quicker than wool, merino, and cotton. For example, if you fall into a river while doing a crossing, which is a dangerous feat to do alone in winter as I have done, you will dry out quicker than if you were wearing merino, but using cotton as a base layer is worse! Cotton will kill you through hypothermia in such circumstances. However, the serious disadvantage with polypropylene is that it’s a plastic polymer, and if while drying out next to the fire that you started to keep warm it catches alight, you now run the risk of serious burns if you get sparks near it. Needless to say, wearing a plastic base and getting these burns will really ruin your day when you’re miles from anywhere, so bear that in mind when selecting this material as your base layer, although sometimes you can find a mix of cotton and polypropylene, though that’s just as bad in my opinion. However, the material has good wicking ability and breathability, along with good insulating properties. This is a viable low-cost option for people starting out or on a fixed budget, and it dries very quickly when wet, but it feels “colder” than Merino or other wool base layers. My recommendation is avoid polypropylene, if at all possible.

2. Merino

Merino is the process of refining raw wool from Merino ewes and then spinning and weaving the wool into light but very durable garments. Note that Merino wool is very different from other wool types. Merino is soft and has low or no itch, which is common with coarse wool of nearly all other types of sheep. Merino wool is just as light per gram in weight as other garment fibers such as nylon, cotton, rayon, and others. Also, the benefit of using Merino for a base layer is the well-known insulating properties of wool. Merino though has the extra ability of being very light when worn next to the skin while trapping warm air molecules between the wool and your mid layer. When worn with a merino base layer and a mid layer on top, you will get the feeling of maximum instant warmth. Going back to the falling in the river scenario, Merino wool base layers will keep you warm while being wet. Even soaking wet, the base layer can be dried off near a camp fire and will not go up in smoke like the polypropyline base will, not to mention the benefit of having the risk of serious burns to your skin eliminated. Also, Merino has the ability to stretch to a high degree. For example, I normally am a 40-inch waist in jeans and cargo pants, but with the Merino base layer I use a size “L”. So take care when buying a Merino base layer to allow for the stretch and for a better fit as a next to skin layer. Note also the Merino wool base layer, when held up to the light, will appear very thin. Merino by its nature is a very thin wool fiber compared to other wool fiber, so don’t be alarmed if the strands don’t seem strong or warm; the contrary is true. Note:there are other heavier wool base layers, such as the surplus thermal base layers, but many people are allergic to the heavier wool thermal layers, so next we come to the late player to enter the market..

3. Tencel

Tencel® is the registered trade name for lyocell, which was developed over the last two years. It’s a biodegradable material made with wood pulp from sustainable tree farms (eucalyptus). Tencel textiles are created though the use of nanotechnology in an award-winning closed-loop process that recovers or decomposes all solvents and emissions (99.5 percent). The greatest benefits are the variety and exceptional comfort you can experience with Tencel clothing. The wood pulp cellulose comes from waste trees from countries that suffer soil degradation and that will not grow normal, slower growing hardwoods and native timbers in subropical climates. Fabric sold under this brand specifically is often mixed with other fibers, such as Merino, silk, and cotton. Being made using wood fiber, it has the inherent well-known insulative properties of wood. Combine this aspect with Merino wool, and you have a product that is warm, easily washable, long lasting, and does not have the property of being flammable. For example, in the last two years there has been more thermal layers coming on the market that combine Merino wool (60 percent), Tencel (30 percent), and Elastane (10 perent); this gives the fabric more stretch and ability to keep shape after being washed in a normal washing machine. Tencel itself is anti-bacterial and will absorb 50 percent of its weight in water, making it ideal for mixing with wool. It is wrinkle resistant and has a very smooth, silky feel to it, which is great news for millions of people who cannot tolerate the itch of wool on the skin. Many, many people are allergic to wool on bare skin, but adding Tencel with Merino eliminates the itchy feel and allows the skin to breathe naturally. What are the disadvantages of Tencel? It will shrink 3% in the first wash but have after that have no shrinkage and the material is more costly to produce than other fibers but will pay for itself in longevity. (I have used my Merino/Tencel thermal layers for consistent winter use for the last two years with minimal signs of wear.)

Recommendation for Layering

My personal recommendation for layering when hiking or going bush is generally using four layers– a base layer (against the skin), a close body layer, a mid layer, and an outer shell layer. For example, I usually wear the following:

Remember you can cool down or keep warm by removing a layer as you see fit. Body core cooling must be avoided at all costs due to hypothermia, and sweating must be avoided also. Even with all of these layers I use it makes for very light clothing, allowing for maximum enjoyment of the outdoors without big bulky clothing such as heavy bonded fleece jackets and work type clothing that one normally finds in Kmart and other big box stores.


So when selecting your next SHTF thermal base layer or just hitting the trail on your upcoming adventure to try out some of your latest preps, try using Merino wool with Tencel as a base layer; I guarantee you will be surprised at the lack of itch, the warmth, and the great feel of using Tencel with Merino, plus you are doing something for our planet! I haven’t discussed pants and how to layer for your legs. That comes in part two, so stay tuned for further reading about Tencel. Blessings