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As any outdoors fan will know, a sharp, versatile knife is worth its weight in gold. Whether you are only heading outdoors occasionally or have a go-bag ready at all times, a good knife needs to be part of your essential equipment list. To keep your knife working well for a long time, we have put together a guide on carbon steel knife care. We will also tell you how to clean your carbon steel knife.
Carbon Steel vs Stainless Steel
To extend the lifetime of your carbon steel knife, it is worth understanding a bit more about how carbon steel and stainless steel knives are made. Steel is an alloy, or a compound made up of several ingredients.
Just like chefs can adjust their recipe for your favorite dish, knife manufacturers can add or remove individual materials from their steel as well as adjust their quantities. This helps adapt not only the steel but also the final product to our needs.
The main ingredients in carbon steel are iron and carbon. There are usually other ingredients as well, but those two need to be present to make a carbon steel knife. Stainless steel knives also contain chromium. As soon as the steel contains more than 13% chromium, it is considered stainless.
Carbon steel knives are considered high-carbon if the carbon exceeds 0.6%. Very few carbon steel knives contain more than 3% carbon. Carbon steel is the more traditional of the two materials, having been used for centuries until stainless steel was invented.
Carbon Steel Knife Care
Caring for your carbon steel knife properly allows it to retain a sharp edge better than a stainless steel knife can. This is one of the reasons why carbon steel knives are so popular for outdoor use. However, to take advantage of that characteristic of the material, you need to get in the habit of looking after your knife more than you are perhaps used to.
Cleaning Your Blade
Keeping a carbon steel blade dry and clean is the key to optimizing its use. Get in the habit of wiping it clean and dry even if you need it again in a few minutes. This will prevent rust from forming on your carbon steel blade.
It may seem perfectly innocent to slice a tomato for your lunch, but anything acidic is particularly tough on your blade. Wipe it dry as soon as you get a chance.
Watch for the Patina
Over time, your carbon steel knife will develop a gray-blue or even black patina. It will start to look like an heirloom or something you use frequently. There is no reason to worry: whilst rust is a bad sign, patina is not only normal, but it is good for your knife. A healthy patina makes it harder for rust to take hold.
The patina on your blade is similar to the green patina that copper roofs develop over time. A good and old patina is often blue, gray or black, and can be seen on a blade that is rusty, but not a lot of rust is present. Orange or red is often a sign of rust, which needs to be removed.
Choose the Right Knife
The higher the carbon content of your knife, the more susceptible it will be to rust forming. If you are going to use your knife mostly outdoors, choose a carbon content between 0.3 and 0.8%. Those will give you all the benefits of a high-carbon steel knife and are easier to take care of.
A higher carbon content makes your blade more reactive to rust. Being outdoors means you may not always be able to look after your knife immediately, which means rust has time to take hold.
How to Clean a Carbon Steel Knife
In an ideal world, you try to prevent corrosion from happening to your knife. However, outdoor activities do not always go to plan. Something as simple as leaving your knife outdoors overnight is often enough to start rust forming on the blade.
Rust develops with exposure to water and oxygen. High humidity speeds up the corrosion process even further. The good news is that rust stains on a knife blade are generally only superficial. Removing those stains has more to do with preventing contamination of anything you want to cut with your blade than protecting the steel itself.
Left too long, rust can start to decay the knife blade. As a consequence, your carbon steel knife may lose some of its strength if you cannot remove the rust.
Removing Rust From a Carbon Steel Knife
There are several ways of removing rust from a knife blade. Done right, neither of them should damage your knife. Saying that you can do damage if you are unfamiliar with cleaning knife blades or are simply overdoing it.
Removing rust from a carbon steel knife blade requires using an acidic material to separate the oxidized iron (rust) from the actual blade. You may also need an abrasive to help grind off rust particles. Carbon steel blades can be damaged by acidic materials and balancing the cleaning materials is very important.
Method 1: Baking Soda
Baking soda and a scrubbing pad are an excellent combination to help clean your carbon steel knife. Start by cleaning your blade with a cleaning solution and a cloth. Avoid using water because this increases the risk of more rust forming on your blade. If you have to use water, make sure you dry your blade very well.
Now mix baking soda with a little water to form a paste. Apply the paste to one side of the blade and wait. If your blade is barely stained, five minutes may be enough. If there is a serious amount of rust, anything up to 30 minutes may be necessary.
Now scrub the blade using a scrubbing pad or steel wool to remove the corrosion. Once one side is clean, wipe off any excess baking soda paste and continue on the other side.
If your knife was very expensive or has a particularly nice finish, you may want to use something softer than a scrubbing pad or steel wool. Scrunched-up aluminum foil or the cork from a wine bottle works well. However, the process will take much longer.
Once both sides of your blade are clean, apply a small amount of mineral oil for additional protection. If you are using your knife to cut food, make sure to choose an oil that has a food-grade rating. Lastly, scrubbing your blade like this can dull your knife, so make sure you check and, if necessary, resharpen your blade.
Method 2: Potatoes
Using potatoes to clean a knife blade may sound strange, but this method is the gentlest choice. For particularly valuable blades and finishes, it is well worth trying this first.
This is what you do: stick your carbon steel knife blade carefully into the potato. Make sure all rust stains are covered by potatoes. Leave the blade for about an hour before removing the knife from the potato. You should now be able to remove the rust with only a soft sponge.
There is no danger of marking the blade or causing additional damage with this method. To finish off, apply a little mineral oil and sharpen your blade.
Method 3: Vinegar
The vinegar method is the opposite of the potato cleaning method. It works on severe blade rust but is also the riskiest of these cleaning methods.
Similar to the baking soda method, start by cleaning your blade, ideally without water. Make sure it is dry before you continue. Next, soak a paper towel in white vinegar and wrap it around your blade. Set yourself an alarm: the blade should only be in contact with the vinegar for anything up to five minutes or less.
Left longer, your carbon steel blade will be permanently stained and perhaps damaged. Once you have removed the paper towel, carefully wipe the blade with a sponge. Should there still be traces of rust, consider following up with the baking soda method.
As with the previous methods, finish off with mineral oil and resharpening.
Some manufacturers have started offering specialist rust erasers. The idea is that they have enough abrasion to remove rust but will not cause damage to your treasured blade.
Carbon steel knives have a history going back centuries. They are an excellent tool for outdoor applications and retain their edge better than a stainless steel blade will.
With a bit of regular care, they will last decades and perhaps even generations. Plus, if rust does start to form on your blade, there are several simple ways of removing it, leaving your blade as good as new.