Why Wool Made a Burden in Camp
Wool can trap still air between its fibers, helping slow the loss of body heat. But in an early sleeping bag, that insulation came with a practical cost: wool filling was bulky, and a bag made with it could weigh heavily on anyone carrying it between camps.
Moisture made the load worse. A sleeper releases water vapor while breathing and sweating, and a tent or shelter can let in damp air or rain. Wool can absorb moisture into its fibers; once wet, a thick filling holds extra water and takes time to dry. That matters on a trip because a damp bag is not just heavier—it is harder to pack and may be uncomfortable to sleep in again before it dries.
The Tradeoff Behind Lighter Bags
A sleeping bag has to do two jobs: keep warm air around the sleeper and remain manageable to carry. Wool favored warmth and a familiar, readily available material, but its bulk and moisture retention worked against portability. Later lightweight fillings made it easier to reduce the carried load, though every insulation choice still involves tradeoffs among warmth, weight, moisture, and durability.
The difference is tangible on the trail: insulation that seems cozy at camp can become a burden when it has to be hauled, damp, to the next one.
