The remarkable characteristics of Damascus steel became known to Europe when the Crusaders reached the Middle East, beginning in the 11th century.
They discovered that swords of this metal could split a feather in midair, yet retain their edge through many a battle with the Saracens.
The swords were easily recognized by a characteristic watery or ”damask” pattern on their blades.
Such blades were reputed to be not only tough and resistant to shattering, but capable of being honed to a sharp and resilient edge.
The original method of producing Damascus steel is not known. Due to differences in raw materials and manufacturing techniques, modern attempts to duplicate the metal have failed.
For eight centuries the Arab sword makers succeeded in concealing their techniques from competitors -and from posterity. Those in Europe only revealed that they quenched in ”red medicine” or ”green medicine.” A less abrupt form of cooling, according to one account, was achieved when the blade, still red hot, was ”carried ina furious gallop by a horseman on a fast horse.”
Writings found in Asia Minor said that to temper a Damascus sword the blade must be heated until it glows ”like the sun rising in the desert.”
According to Dr. Nickel, once blades of Damascus steel had been rough-shaped by hammering, they were ground to a fine edge. When they were hammered chiefly on one side, a curved shape resulted – the origin of the sabre, he said.
The finest blades ever made, he added, were the Samurai swords of Japan, whose blades may contain a million layers of steel. The layers resulted from hammering out a bar to double its original length, then folding it over as many as 32 times.
The multiple layers used by the Japanese and by makers of the Malay dagger or kris are sometimes referred to as ‘ ‘welded Damascus steel.” Although the production method differs from that of true Damascus steel, the blades may show a very similar pattern.
from a 1981 article by Walter Sullivan and Wikipedia