Blade Patterns... What is Damascus Steel?
First, lets understand a bit about the forging process. There are essentially 2 ways to shape a blade: Forging and Stock Removal.
What is stock?
Stock or Bar Stock also known as a blank, slug or billet is a form of raw purified metal. Common shapes are round bar (also called rod), rectangular bar and hexagonal (also called a hex bar).
So in (very) simple terms, stock removal is taking a bar of steel and getting rid of the excess which then forms the shape of a blade. there are many ways to remove steel: Machining, Milling, Grinding, Filing, Sawing etc.
When it comes to forging, things get alot more interesting. A forged blade is shaped by heating the steel to between 1800°F-2100°F known as the plastic stage, and then using a hammer or press to work it until its close to its final shape. Refinement is often done on the grinder (like a belt sander), and edges are finished and sharpened on whetstones.
Ok, Damascus. There are many theories on its origin, contentious ones at that. but for brevity sake, common explanations are that the steel is named after the city Damascus, Capital of Syria. Wootz Steel introduced there came from Southern India and Sri Lanka. Some interesting reading can be found on "Crucible Steel" and Wootz Steel. Dating back to the 1st Millenium BC. I'll do another blog on the actual manufacturing process.
Back to Patterns!
Metallurgy and Chemistry form the basis here.As an example, Various Steel types are welded together to form a billet. a very common combination is 1095 and 15N20. Heated then folded or twisted, sandwiched etc. each technique resulting in a layered (sometimes into the hundreds of layers) blade. Its tempered, quenched and etched in acid. I know this is a very over simplified example - and i will do another more detailed write up on this - but we are talking about patterns!)
So the acid bath is what brings those distinctive and unique patterns to life. There are MANY MANY patterns and each bladesmith can have their own style in producing effects on the blade. Below are some examples:
There are many more.
Fire, Feather, Fishbone, Fireball, Random...