Pattern welding is the practice in
sword and
knife making of forming a blade of several
metal pieces of differing composition that are
forge-welded together and twisted and manipulated to form a pattern. Often called (Modern)
Damascus steel, blades
forged in this manner often display bands of slightly different patterning along their entire length. These bands can be highlighted for cosmetic purposes by proper polishing or
acid etching. Pattern welding was an outgrowth of
laminated or piled steel, a similar technique used to combine steels of different
carbon contents, providing a desired mix of hardness and toughness. Although modern
steelmaking processes negate the need to blend different steels, pattern welded steel is still used by custom knifemakers for the cosmetic effects it produces.