Damascus
Pattern-welded layers, folded and forged.
Layers, not luck
Damascus is two steels — one bright, one dark — forge-welded into a stack, folded, and drawn out. The pattern is the layers, revealed when you etch the finished blade.
How it's done
stack alternating 1095 and 15N20, welded fold each fold doubles the layers draw stretch and re-stack, keep the weld hot etch acid bites the two steels differently
Why smiths love it
Partly it's beautiful. Partly it's a test — every fold is a chance to fail at the weld. A clean damascus blade means two hundred heat-cycles went right. That's a signature, not a decoration.