A soft, fitted cap traditionally worn to bed to prevent heat loss from the head during sleep. Historic versions were often made of wool or heavy cotton with a long, pointed tail, sometimes ending in a tassel. While largely obsolete for warmth due to central heating, variations made of silk or satin remain in use to protect styled hair or prevent tangles overnight.
Heard on the job
I'm sewing a silk nightcap to keep my curls from frizzing on the pillowcase.
Insider tip
When sewing a sleep cap for hair protection, the smooth side of the satin must face inward against the hair, not outward for show.