1. Why Are Knife Steels Named After Paper Colors?
At first glance, "White Paper" and "Blue Paper" steels might seem to refer to the color of the metal. However, the steel is not colored. The name comes from the paper wrapping. When the steel was produced, white or blue paper was attached as a marker to identify the type [1]. This system was used by the manufacturer as a visual cue to tell the steel types apart. Other retailers also describe this practice of using colored paper to separate the steel types [2]. These names are still used as trademarks today. Think of it as the "shipping label color" of the steel. The label makes it easy to spot, but the paper color itself does not determine the steel's nature. To understand the performance, we must look at the chemical composition.
2. What Is Inside White Paper Steel?
"White Paper" steel is a high-purity carbon steel. It has very few impurities or alloying elements [3]. You can think of it as iron mixed with only carbon. There are three grades: No. 1, No. 2, and No. 3. The difference is the amount of carbon. For White Paper grades, No. 1 has about 1.25–1.35% carbon, No. 2 has about 1.05–1.15%, and No. 3 has about 0.80–0.90% [3]. A higher number does not mean "better"; it simply means less carbon. To visualize this, imagine a 100g piece of steel. In White Paper No. 2, the carbon weighs about 1.1g. Since a 1-yen coin weighs 1g, that is just a little more than one coin’s worth of carbon mixed into the iron. White Paper No. 1 has about 1.25–1.35g, which is about 0.2g more than No. 2, and that 0.2g is the difference of one number. The key point is that White Paper has almost no notable additions besides carbon. But what happens if we add other elements? That leads us to Blue Paper.
3. What Is Added to Make Blue Paper Steel?
"Blue Paper" steel starts with the same pure carbon steel as White Paper, but two elements are added: chromium and tungsten [3]. Blue Paper No. 1 and No. 2 have roughly the same carbon content as their White Paper counterparts, but with these additions [3]. For Blue Paper No. 2, the composition is approximately 1.1% carbon, 0.2–0.5% chromium, and 1.0–1.5% tungsten [4]. Note that ranges vary slightly depending on the source, so we use "approximately." In a 100g piece of steel, the tungsten weighs 1–1.5g (about one to one-and-a-half 1-yen coins), and the chromium weighs 0.2–0.5g (less than half a coin). Together, these added elements weigh about 1.2–2.0g per 100g of steel. Since the carbon amount is the same as White Paper No. 2, the total difference in ingredients is at most about 2%. There is also a higher grade called "Blue Paper Super," which has more carbon (1.4–1.5%) and tungsten (2.0–2.5%), plus molybdenum and vanadium [4]. The name "Blue Paper" covers a group of steels whose contents differ by number and series. But how does adding just 2% change the knife? Let’s look at the effects.
4. How Do Tungsten and Chromium Change a Knife's Sharpness, Sharpening, and Rust?
Tungsten creates hard particles that resist wear, helping the edge stay sharp longer [2]. Chromium affects how easily the steel can be hardened and its toughness [2]. The main feature of Blue Paper is that it has higher wear resistance than White Paper. However, there is a trade-off. White Paper is easier to sharpen and can take a very fine edge, but it is said to be more prone to chipping. Blue Paper is more wear-resistant, but it is slightly harder to sharpen [1][5]. Neither is "better"; they just have different strengths. Regarding rust, Blue Paper rusts just like White Paper. The chromium in Blue Paper is only about 0.2–0.5%, which is far below the roughly 10.5% or more that a steel needs to be classed as stainless [5]. Even at the highest amount, it is only about 1/21 of that level. Both White and Blue Paper rust easily, so you must wipe them dry after use. There is another type called "Silver Paper" that is more rust-resistant [1]. Finally, the material is not everything. Sharpness and durability depend on forging, heat treatment, material, and sharpening [6]. Two knives made of the same Blue Paper steel can feel very different depending on the maker and how they are cared for. The ingredient list shows trends, but it is not the whole story.
5. Where Are White, Blue, and Silver Paper Steels Made?
"Yasugi Steel" is a brand made at the Yasugi factory in Shimane Prefecture. It includes the White, Blue, and Silver Paper series [10]. Yasugi is known as a "Steel Town" because it is blessed with sand iron and a good harbor, and tatara steelmaking has been active there for a long time [7]. In 1899, five entrepreneurs in Yasugi established the Unpaku Iron and Steel Joint Stock Company [7]. This company became the Yasugi Steel Works in 1916 [8]. In 1928, the president, Kudo Haruto (1878–1963), developed a method to make sponge iron from sand iron. This led to the production of Yasugi Specialty Steel using electric furnaces [8]. "YSS" stands for Yasugi Specialty Steel and is the trademark for Yasugi Steel [9]. Production later moved through Hitachi Metals, and since 2023, it has been handled by Proterial. White and Blue Paper are still produced [9]. However, the sources do not state whether the raw materials for current White and Blue Paper are sand iron. It is safest to view the town’s history as the background for where the name was born.
6. How Can You Check the Steel Name on a Knife's Material Label?
Look at the material section of your home knife or the knives in a shop. Check if you see names like "White Paper," "Blue Paper," or "Silver Paper." If you find them, you can recall the numbers from this article to understand if it is a carbon-only steel or one with added chromium and tungsten. Remember, forging, heat treatment, and sharpening also play a big role [6]. Always handle blades with an adult. After use, wipe the knife dry. Both White and Blue Paper steels rust easily [1]. The remaining question is: How much does the maker’s skill change the personality of a knife, even if it has the same "Blue Paper" name?