Tuesday, March 27, 2018

Wait, you WANT it to rust?

We've been conditioned to view rust as the enemy of all things steel. That's actually pretty good advice, on the whole, but sometimes you can guide rust to actually protect your steel. In those instances, it is called a patina, and a great example of this is the bluing process used on firearms.

One of the big weaknesses of many knives, including several varieties of Mora, is that their carbon steel blades are susceptible to rusting. This vulnerability can be exploited to protect the blade and is actually very easy to do.

Rust, that uncontrolled red nightmare, is ferric (iron) oxide. When properly controlled, this oxide forms a thin, protective layer on the surface of steel and iron products. It's pretty simple to control this process, and relatively safe, with the side effect of giving your blade a very cool muted gray color. It's also a food-safe finish, keeping all the utility of your knife.

There are a variety of techniques to patina a blade. Many involve harsh chemicals, and while they work well, I'd rather avoid those since there is a safer, less costly, and more convenient method using only household products. You simply need a cleaner (rubbing alcohol is the general favorite), an acid (mustard, citrus juices and the like will work, but vinegar is cheap and effective), and a bit of time.

This video shows a cold patina method, which is the safest way to proceed, but takes more time and doesn't give as deep or even a finish:

The hot patina method gives a faster, deeper finish, but requires handling a boiling acid, and taking the appropriate safety measures:

There's also this method, which uses hydrogen peroxide as a rust accelerator, promoting a fast, deep patina. It is a bit more involved, but also gives the best results.

Choose whichever method you're most comfortable with, and protect your steel. It will serve you well for a lifetime.


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