Why can a silk pillowcase feel cool the first moment your cheek touches it even when the pillowcase is already at room temperature?

Answer: Faster heat exchange

Colder stored fabric — This is the tempting guess because your skin reports the sensation as cold. But a silk pillowcase left in the room is normally near room temperature, not secretly chilled. The feeling comes from a brief heat-flow imbalance: your warmer cheek loses heat into the textile faster than it would into a fluffier, lower-contact surface.

Faster heat exchange ✓ — Correct. Cool touch is mostly a transient heat-transfer signal, not proof that the silk is colder than the room. Textile labs describe this with thermal effusivity or effusance: a surface that can take heat from skin quickly feels cooler at first contact. That is why metal, stone, and some smooth fabrics can feel cool even when a thermometer says they are the same temperature as nearby objects.

Hidden surface moisture — Moisture can change fabric comfort, but it is not needed for the first-touch silk effect. Dry textiles still differ in how quickly they exchange heat with skin. If surface water were the main cause, the pillowcase would feel clammy or damp; the common silk sensation is usually a dry, smooth coolness.