Bluing v Forced Patina - Kitchen Knife

[jameson1881]

I'm making some kitchen knives with 1080 steel and want to use a bluing sort of process to prevent rust. Is there a good food-safe way to bue or am I looking for a forced patina? Recipes would be greatly appreciated either way!

[Steve Sells]

why not hot bluing?

[Frosty]

Welcome aboard, Jameson, glad to have you. If you'll put your general location in the header you might be surprised how many members live within visiting distance.

Bluing IS patination. Some patinations are more durable than others, I recommend to you: "The Coloring, Bronzing and Patination of Metals," by Richard Hughes. It has more than you'll even need to know about the subject start to finish and in close detail.

Frosty The Lucky.

[jameson1881]

Frosty thank you for the resource! I will certainly update the profile but first I have some reading to do. Steve hot bluing is what I was initially trying to research but I am a complete rookie to the process so just looking for information at this time. 

[rhitee93]

Carbon steel blades will oxidize over time with any practical level of care.  The idea is to get them to oxidize with forms of iron oxide other than red rust as they are less problematic, and tend to extend the time it takes for red rust to form.  Many of them happen to look pleasing as well which is a bonus.  To my knowledge, there is no concern with bluing and food safety as long as the blade is cleaned of all the bluing chemicals after it is done.

Hot bluing requires a pretty significant commitment to do in the home shop.  Some do have setups, but unless you plan to do a lot of it, you'll probably find the hazards and expense are not worth it.  There may be a gunsmith reasonably close by who can hot blue your parts.

[Irondragon Forge ClayWorks]

I've used cold gun bluing without any problems, however lemon juice does about the same.

[jameson1881]

4 hours ago, rhitee93 said:

Carbon steel blades will oxidize over time with any practical level of care.  The idea is to get them to oxidize with forms of iron oxide other than red rust as they are less problematic, and tend to extend the time it takes for red rust to form.  Many of them happen to look pleasing as well which is a bonus.  To my knowledge, there is no concern with bluing and food safety as long as the blade is cleaned of all the bluing chemicals after it is done.

Hot bluing requires a pretty significant commitment to do in the home shop.  Some do have setups, but unless you plan to do a lot of it, you'll probably find the hazards and expense are not worth it.  There may be a gunsmith reasonably close by who can hot blue your parts.

Thanks for the feedback. I hadn't even considered checking with a gunsmith. There is a shop right in the little town where I live. Maybe I'll pop in with some questions.

3 hours ago, Irondragon Forge & Clay said:

I've used cold gun bluing without any problems, however lemon juice does about the same.

I finished my first high carbon knife about a month ago and it's getting a patina very quickly from all the grapefruit and lime I cut. Maybe on that test blade I'll just "forget" to wipe it down for a few hours and see how it does. Is there any advantage that you know of to citrus over vinegar?

[BIGGUNDOCTOR]

You might get mixed results with hot blues. Some receivers like Krag Jorgensen, Some Winchester lever action receivers, and hardened springs come out more maroonish than blue. This is due to case hardening, nickel content, and hardening. It may come out fine, but I am just preparing you for what might happen. Don't worry about losing tempering as the salts are 292F for gun bluing. 

If there are any crevices the salts will get into them, and leach out later.

You can also do a rust blue. Old firearms were done this way. Parts weer put into a humid cabinet after having a rust forming solution brushed over them. They were removed and any orange rust was carded off. More solution added and the process was repeated until the desired color was achieved.