Sea silk may be the rarest and most mythologized fabric on Earth, and it does not come from a plant or a sheep. It is spun from the byssus, the beard of silky filaments that the giant pen shell Pinna nobilis secretes to anchor itself in Mediterranean seagrass. This episode explains how a liquid protein hardens on contact with seawater, why lemon-juice baths dissolve the tough outer sheath to reveal a glowing golden core, and why it takes the beards of roughly 150 shells to knit a single pair of gloves. It also examines the famous legend of gloves packed inside a walnut shell, which marine biologist Helen Scales traces to a 19th-century marketing stunt involving Limerick kid leather.

From there the story moves through the tangled history of the word byssus, Roman references from Tertullian and Diocletian's price edict, Silk Road myths of gol ...