Those swirls are actually inside the steel.
Pattern welded Damascus steel is made by stacking multiple alternating layers of 2 different alloys that have similar heat treatment requirements, one with a nickle content and one regular high carbon steel. This stack is then forge welded into a homogeneous billet. It is now solid piece that still has it alternating layers. You then cut it up, stack it and re forge weld it together again to raise the layer count. This restacking process is repeated untill the layer count is where the smith wants it. Then the billet gets drawn out and manipulated in various ways like twisting, making cut or drilling shallow holes etc then the bar gets hammered out flat. When a blade is made from the resulting billet of damascus steel it wont look any different from a normal steel blade, untill it gets etched in acid. The nickle in the one steel will resist the acid staying bright while the carbon in the other gets eaten up, turning black.
Sorry for the long post in
@Duggan's thread. Someone asked a question here that I'm actually qualified to answer lol.
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