Achieve Damascus steel style with Cycles so I'm modeling a katana, and I would like to give it a proper "Damascus" style to the blade, and I was wondering if it's possible to achieve this in a way that doesn't involve me opening GIMP/Photoshop.

The desired effect is this:


So far I got this material:

Ignore the red tint.

So my questions are:


How to "mask out" the black so I can control it, and apply the Principaled on top of let's say a brushed metal shader.
Is there a way I can make the noise/musgrave/voronoi start in stripes and then go wavy? Maybe aWave texture and use a ramp to fade them?


Thanks for any input!
Final



Node setup

Setup is fairly easy to understand. We will use only Wave Texture with Distortion controlled by vector driven by Color Ramp. Then we will use output of this for Roughness in Principled BSDF.

First Color Ramp (left one) can be used to control how many stripes should be on bottom of the mesh and blend between stripes and pattern. Black is straight, white distorted. Second one controls Roughness value and here colors are important. Black is shiny, white is matte. 



Output of the texture



Final with UV mapping and mask for blade