Damascus steel is a type of steel developed and used for centuries in India and the
middle east before the secret of its forging was lost (ca 1800). It became known to europeans during
the crusades, when they came up against
Saracens with swords far superior to their own.
Damascus steel was known for its strength, flexibility, and ability to hold a fine sharp edge. Swords made from Damascus steel could allegedly be bent tip to hilt without the sword breaking, yet hold an edge sharp enough to cleave a silk scarf in two -- or cut a man in half with a single stroke.
Damascus steel also had a distinct appearance -- hundreds of wavy lines or alternating light and dark patterns marked the surface. This shimmering watermark effect was the result of residual carbon (dark) and bonded iron carbide (light) in the steel. This effect was often enhanced by acid-etching of the blade.
The secret to forging this steel was jealously guarded by Islamic artisans. Only incomplete records are left to us today. Scientists have duplicated the properties of Damascus steel, but find it to be a labor-intensive process that requires repeated folding of the steel and the proper amount of impurities -- especially vanadium.