I'm trying to force a patina on a Hontanren Iron clad wa gyuto. I love this knife and would like to force a patina on it. Does anybody have a suggestion for the best results for the soft iron. I tried beef blood and which had some decent results but when I checked it there were a few serious rust spots. Once I removed the rust the patina was almost gone. I'm trying the mustard patina now in short intervals and after 5-8 minutes there is only rust and no real patina to speak of. If anybody has any other tips or techniques I would love to hear them.