Chemical
Stale urine (lant)
Stale urine (lant) → Woad blue
Picture to come.
Urine collected and left to stand for days or weeks, during which it becomes strongly alkaline. Dyers used it in fermentation vats for woad, where the alkaline, bacterially active liquid dissolved the blue dye so that it could take on wool; cloth turned blue as it dried in the air. The word derives from Old English. How far 12th-century English dyers relied on urine rather than other alkalis is uncertain.
Caveats (confidence: medium)
The consulted study documents historical urine-based woad vats but gives no specific 12th-century English evidence. Other uses (e.g. scouring wool) are omitted as unverified.
Sources: sciencedirect.com
Made by
- Collect stale urine
Used to make
- Ferment a woad vat