I have a Western W49 bowie knife ( I know, I know, but it works real hard out in the sagebrtush hills of southen California.) I finally wore out the old sheath, and had a leathersmith make a custom one. I believe the chemicals used in the tannig process are causing discoloration of the blade. Is there any way to neturalize this process? Any help is appreciated as this knife and I have been real close for many, many years....thanks