The cooling effect in high-performance sleep products is not magic or marketing. It is physics. Here is how cooling technology actually works and why some materials perform dramatically better than others.
Thermal Conductivity: The Key Property
Every material has a thermal conductivity, a measure of how readily it allows heat to pass through it. Materials with high thermal conductivity like metal feel cold to the touch because they rapidly draw heat away from your skin. Materials with low thermal conductivity like cotton and polyester feel warmer because they resist heat transfer, trapping it against your skin instead.
Cooling sleep products are designed to use materials with high thermal conductivity so that body heat is drawn away from your skin and dissipated outward rather than being trapped under the bedding. The Q-Max score is the measure of this: above 0.35 means the material is genuinely thermally conductive enough to provide a sustained cooling effect.
Why Nylon Is the Best Cooling Fiber
Among materials suitable for blanket construction nylon has unusually high thermal conductivity for a textile. It also has a smooth surface that maximises skin contact for efficient heat transfer, and excellent moisture-wicking properties that draw sweat away from the skin rather than holding it against you. The combination of high Q-Max, smooth surface, and moisture management is why nylon consistently outperforms other blanket materials for hot sleepers.
The Moisture-Wicking Mechanism
Moisture wicking works through capillary action. The fiber structure of nylon allows moisture to move along and through the fiber from areas of higher concentration, your sweaty skin, to areas of lower concentration, the outer surface of the blanket where it can evaporate. This keeps the skin dry even during sweating episodes and reduces the clammy discomfort that compounds the heat problem for hot sleepers.
The Stillwell Cloud is engineered around both of these mechanisms. See The Cloud here.