Differential Bluing?

[Chuck Gedraitis Knives]

I know that you can determine where you etch damascus, and anodize titanium by using nail polish. Can you also use this to differentally cold blue a knife blade? I will be experimenting, but wondered if anyone had tried this?
Thanks
Chuck

 

[peter nap]

Yes Chuck you can. I didn't use nail polish, I used shellac I think, but anything to keep the blue off the steel.