Comfort and Moisture Transport in Lightweight Wool and Synthetic Base Layers

Same here, Eins.

But I'm glad because this was a good read. Your 2007 post is interesting and possibly calls for an answer from those who tested the swatches. Strangely, the conclusion drawn from your calculation is completely at odds with my experience. After a run I feel an urge to get out of a merino top within 30 seconds of getting back home because the heavy weight of cold sweat feels horrible against my skin. In the only synthetic top I have left, after ending the run, I can keep it on long enough to prepare a recovery drink and run a bath.

No one has mentioned getting a hot, sweaty back under a rucksack. I was one shouldering long before reading about it in Beyond Backpacking because I can sweat enough over a couple of days of backpacking to cause nappy rash. I find merino particularly unpleasant against the skin of my back when a day's walking has turned uphill and aerobic. It really itches when warmed up a bit.

Merino has numerous, clear disadvantages so why do I prefer it? On my last Pyrenean hike I had a Capilene T-shirt and a Smartwool long sleeved top. I had thought that the T would be the garment I walked in and the merino top would be for evenings. That is not what happened. The T-shirt became so stinky within half a day that I could not stand it. (One of the 2006 posts mentions this problem. I wish I'd read it back then.) The merino went on and stayed on day after day without becoming unpleasant.

There must be something physical and measurable, apart from lack of stench, which accounts for my preference for merino. Perhaps it's to do with the drape. Merino feels more classy, somehow.

By the way, synthetics do wear away. Mine became thinner and thinner till all that was left was a net of fine fibres. The seams on synthetic tops have always had a tendency to carve away at my delicate skin, particularly round the armpit, and this becomes much worse once the top is a bit worn.

Best wishes.

Great info here! Anyone have additional comments about using a long sleeve merino baselayer to block sun and keep cool, especially in more or less low-humidity conditions? I took a white Zensah compression shirt on a Kilimanjaro trek in 2007, and just last week to Muir on Rainier. The compression shirt is fantastic at blocking/reflecting the sun and acting almost as an air conditioner. Any sweat evaporates immediately, keeping me nice and cool. And since it's a compression shirt, this is the case for every square inch. No baggie sleeves to trap air – which seems to me would allow heat build up and impair wicking. So the only drawback on the white compression shirt in that setting is, of course, the stench. Zensah uses an antimicrobial treatment. But while the stink is reduced (and kind of a different, slighlty less pungant odor) than your typical untreated wicking synthetic, it's still there, still pretty objectionable. Meanwhile my Smartwool midweight that I also wore off and on all week has no discernable odor. So now I'm looking at Rapha's white merino baselayer or Smartwool's microweight in silver. I gather merino's wicking is better, but evaporation is not as good. Is the evaporation enough poorer that I'll go from feeling air-conditioner-like properties to feeling like I'm wearing a thin but soggy insulating layer? Anyone have any experience with the newer generation UnderArmour heatgear? It claims antimicrobial properties – does it fight stench as well as merino? Thanks!

Thanks Paul! Good to know. I suppose it's a question of finding something that works in a certain range of conditions. A merino baselayer might fail in hot/humid conditions (while a synthetic compression shirt is able to keep up evaporation-wise). But I suppose on a glacier with ambient air temps of 20-40 degrees yet brutal sun, the merino's evaporation performance will be adequate to give me that effect.