Why can a thin silk sheet feel cool at first touch but still fail to keep you cool all night under a warm blanket?

Answer: Touch and insulation differ

Touch and insulation differ ✓ — Correct. First-touch coolness measures how fast the surface takes heat from your skin at the beginning. Overnight comfort also depends on whether heat and moisture can leave the bedding system. A thick blanket can trap warm air around the body, so the sheet can win the first second and still lose the all-night comfort contest.

Silk stops conducting heat — Silk does not switch off its thermal properties after you lie down. What changes is the heat gradient and the larger bedding environment. Once the contact area warms up, a low-ventilation blanket stack can keep heat near you even if the sheet felt cool at first.

Fiber content alone rules — Fiber content matters, but it is not the whole comfort system. The same fiber can be woven, knitted, brushed, layered, or compressed in ways that change air gaps and vapor movement. The better lesson is a split between two tests: cool hand feel is about early contact, while sleep comfort is about the whole layered system.