Boiled leather, sometimes called
cuir bouilli, was a historical construction material for
armour. It consists of thick
leather, boiled in water. According to some sources boiled
oil and
wax were used as well, while others posit the use of
ammonia from fermented animal
urine. The boiling causes the leather to become harder but also more brittle. The boiled leather can be fashioned into lames or
scales to make
lamellar or
scale armor. The leather remains flexible for a short time after boiling, allowing it to be molded into larger plates.