Undershirt

Close to the skin and close to the heart. The most important function of the base layer - to keep moisture off the skin of your torso - makes it a crucial part of the gear.

A favourite of mine, the thin and light merino wool shirt Kent, from Icebreaker. The pack is filled to bursting with 8 days of food and gear.

The Kent; faded but still going strong after three hiking seasons. Other merino garments have not lasted more than a quarter of that time. And no, I do not get paid for saying this.

I almost always carry an extra base layer shirt, for use at night and as an extra layer while hiking, if the weather should turn really chilly. With a hood like on this one (BPL Merino Hoody), I do not need to bring a warm cap.

Comments and current insights: Even if my current favourite is a wool (under-)shirt, I have used synthetic base layers a lot. For several years I used light and cheap 100% synthetic shirts that I bought at the mall. They worked very well and if you hike in a warm climate they are easy to rinse out every day, since they dry out in a jiffy. But more on this in the book. I always sleep in my underwear and sometimes more. When sleeping, I appreciate not having a sweat soaked undershirt from the day's hike next to my skin; so I use the extra base layer garment for this.