My understanding of Japanese knife steel is White #1 which has virtually no additives, White #2 has minimal additives Blue #1 with slightly more additives Blue #2 again more additives and Blue Super with the most additives of any.
These additives are put in to increase durability, add toughness (not to be confused with hardness)and more corrosion resistance, although none are stainless.
The name is said to come from the color of the paper the steel is traditionally wrapped in.
So the trade offs go from White #1 which is said to be able to get the sharpest but has the least edge holding ability then on up the “ladder”.
Keep in mind, these steels are all excellent carbon steels and the differences are very slight, maybe not even noticeable for a novice like myself.
There are also many opinions on which is the best depending on the quality of heat treating, and the type of knife, or individual user.
If a metalurgist is viewing this I would welcome any corrections as this is a simplified explanation.
Glen
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