Why Does My New Knife Have Marks on It?

If you’ve just unboxed your high-carbon steel knife and noticed dark stains or discoloration, you might be wondering if something is wrong. Rest assured, these marks are completely normal and even beneficial in the long run. This natural process is known as patina formation, and it plays a crucial role in protecting your knife.

What Is a Patina?

A patina is the discoloration that forms on high-carbon steel due to exposure to moisture, acids, and other environmental factors. Unlike rust, which can damage the steel, a patina acts as a protective layer that helps prevent corrosion. It can appear in shades of yellow, blue, and grey, depending on the steel type and what it comes into contact with.

Certain types of steel, such as Aogami (Blue Steel) and Shirogami (White Steel), develop patina more quickly. Other metals, like copper and bronze, also form a patina over time, often showing shades of green and blue.

What Causes a Patina to Form?

The patina on your knife begins developing the moment you start using it. Key factors that contribute to patina formation include:

• Moisture – Water and humidity accelerate the oxidation process.
• Acidic Foods – Ingredients like citrus, onions, and tomatoes react with the steel and speed up discoloration.
• Salts – Salty foods can leave behind residues that enhance patina formation.

Even handling the blade with bare hands can contribute to patina development, as natural oils and moisture from fingerprints can react with the steel.

Why Is a Patina Beneficial?

Rather than being a flaw, a patina actually serves as a protective barrier against rust. Over time, as the patina forms and darkens, it reduces the likelihood of rust spots developing. Many chefs appreciate the unique appearance of a patina, as it tells the story of their knife’s journey through countless meals and preparations.

Why Aren’t All Knives Made of Stainless Steel?

Stainless steel knives are easier to maintain because they resist rust and discoloration. However, they are often softer than high-carbon steel, meaning they don’t hold their edge as long. High-carbon steel knives, on the other hand:

• Have superior sharpness and edge retention.
• Can be hardened to a higher Rockwell Hardness (HRC), making them ideal for precision cuts.
• Require more maintenance but reward users with unmatched performance.

For chefs who rely on their knives daily, the extended sharpness of high-carbon steel outweighs the extra care required to prevent rust and maintain the blade.

Can I Remove a Patina?

Yes, if you prefer the look of a clean, polished blade, you can remove a patina using:

• Polishing compounds – Specialized pastes or creams designed for steel.
• Whetstones – Lightly sharpening the blade can strip away surface discoloration.

However, the patina will likely reform after your next use, making removal a temporary fix.

How to Prevent Rust on Your Knife

While a patina helps protect against rust, high-carbon steel still requires proper maintenance. To keep your knife in top condition:

• Wipe the blade dry immediately after use.
• Avoid prolonged exposure to moisture and acidic foods.
• Store in a dry place, away from humidity and salt.

Final Thoughts

Patina development is a natural and beneficial process for high-carbon steel knives. Rather than worrying about discoloration, embrace it as a sign of a well-used and well-loved tool. With proper care, your knife will serve you for years to come, developing a unique character that reflects your culinary journey.

At Chef’s Larder, we offer high-quality knives designed for both professionals and home cooks. Explore our collection and experience the difference of precision-crafted blades.