patination of damascus blades

[Claude Marquis]

I've seen a few damascus blades showing beautiful colors from blue to purple, and even green.
Can someone explain me in detail how these colours are obtained?
Thanks alot for the information.
Claude

 

[Arthur Washburn]

I think the process they are using is Hot Bluing but they are contaminating the salts with some sort of oil and this results in the colors you spoke of.

Arthur D. Washburn
ADW Custom Knives

 

[Ed Caffrey]

Most of the common colors are from leaving the temper oxide on the blades. There are several other methods that I have seen/used with good success. Baking laquer is one, which is nothing more than coating the etched blade and then sanding lightly to remove the coating for the high spots of the topography. One can also add different non-ferrous metal dust/powder to you etchant. Copper will give you the greenish cast, iron will give you reds to organes, and so on. Colors achieved by the last method are very easily worn off. The main problem with adding the dust/powder to your etchant is that you can't clean it out for normal etching. Once it's in there, it's in there!

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Ed Caffrey "The Montana Bladesmith"
ABS Mastersmith
www.caffreyknives.com