I discovered Polypro a long time ago when I was a young man and was overjoyed to abandon coarse itchy wool layers that were the only choice back then. The only downside was the smell; after a few days in the mountains my clothing could be classified as a weapon of mass destruction. I’m sure if my clothes were dropped on a foreign country it would bring them to their knees and they would beg to be freed from the awful stench. At first, washing helped, but after a few months I just needed to wear my Polypro’s for 5 minutes and the neighbourhood would need to be evacuated.
A few years later I discovered women and realised (or did mum tell me?) that polypro and women were not compatible – I was faced with a tough decision. Fortunately I was saved. Super fine merino was becoming available so I incinerated my next-to-skin Polypro and replaced them with this great re-discovered, non-itchy natural fabric.
Many years later I’m now married with two kids so either my wife lacks a sense of smell or my new clothing system has worked. However, a few recent experiences have provoked me to question my thinking that merino next to the skin is the only solution.
Over a 20 year period I experimented with many different merino garments and had settled to always wearing a merino t-shirt. I had tried merino leggings and boxers but found the fabric lacked the elasticity/supporting characteristics required so had resorted to polypro leggings and nylon underpants (cotton is a dismal failure in the mountains).
Disaster struck 3 years ago while I was making the first ski traverse of the Southern Alps. On day 22 at the head of the Rakaia, I developed a bad fungal infection in my nether regions. Too much nylon in those sweaty, high movement areas had reduced me to a whimpering wreck. Fortunately I managed to remember some school chemistry and realised that such problems are caused by salty, acidic environments. By using some alkaline ash from the fireplace I was able to change my skin chemistry and recover.
After giving a talk about my adventures in Christchurch I was given a pair of Earth Sea Sky’s Merino/Lycra Stretch Boxers. I was a bit dubious at first since experience with pure merino boxers were not a success but these were different. They kept their shape and support – without getting into the detail, you boys will know what I mean. The second experience happened recently when I was doing a high ski traverse in the Sierra Nevada in California which involved long days of fast travel and long nights in a small cold tent. I took both an Ultra Fine Merino (17.5 micron fibre) and a polyester Power Dry® Earth Sea Sky Lightweight t-shirt. I expected them to perform similarly but with the synthetic one smelling like my old polypro.
When traveling in alpine environments I pay special attention to the end of the day when you are hot and damp with sweat from a long day’s travel but suddenly stop and cool down as you pitch the tent and get dinner ready. In this situation I would either keep moving vigorously with loose fitting clothing to try and evaporate the excess moisture from my clothing or I would swap out the base merino layer with a dry layer (if I had a dry layer and could handle stripping off in sub-zero temperatures).
To my amazement this problem almost disappeared when I was wearing the polyester fabric – I wasn’t as damp as when wearing merino. One reason is that merino can absorb up to 30% of its weight in water while polyester absorbs at the most 2%. This equated to a difference of about 50 grams of water, which takes a lot of energy to evaporate. Or to put it another way, it removes a lot of heat from your body getting rid of the moisture and while it does this it takes a lot of body warmth to warm 50 grams of water before the water warms you.
My current thinking is that merino and polyester are both incredible fabrics but in winter it is worth questioning where and when they should be used. On long trips when washing is not frequent, natural fabrics such as merino tend to work better around the groin where their anti-bacterial/fungal properties are advantageous. On your upper body where moisture can get trapped, especially under your pack, polyester works well since it absorbs very little moisture and helps you avoid the chills when you stop moving.
Notes to avoid confusion:
- * Polypropylene (Polyprop) is a different fibre to Polyester
- * The surface of Polypropylene is extremely coarse. Contamination from contact with the skin builds up on the fibre surface and washing agents cannot remove this. Eventually the fibre feels oily and no longer wicks moisture from the skin
- * Polyester fibres are very smooth in comparison. Contamination from the skin may temporarily stick to their surface during wear but this is removed by the surfactant action of detergents during a wash
- * Polyester fabric absorbs less than 1.5% of its weight in moisture. Woollen fabric does not feel wet till it is carrying 30% of its weight in moisture. It can absorb more moisture after feeling wet