Creating a Kasumi Finish
While sharpening a Kasumi-finished knife, I often find myself pondering the process of creating that Kasumi pattern. Normally, if you sharpen it with a medium grit stone of around 1000, it starts to develop the hazy Kasumi effect. However, the challenge arises when it comes to the Kasumi on the tip curve. When I try to maintain that curve while sharpening, I always end up with these sharpening marks or lines, as you can see in the photo.
Note: I added the white lines on top of the photo.
The reason behind these lines is a bit tricky to explain in words, but today, I’ll give it a shot! First, knives are three-dimensional, while sharpening stones are flat – that’s the fundamental issue. So, when you’re using a flat sharpening stone to sharpen a curved knife, those lines naturally appear when you consciously try to maintain the curve while sharpening. Does that make sense?
However, there are probably folks out there who say, ‘I want to get rid of these lines! I want a clean Kasumi finish!’ So, here’s the method: you can make those lines disappear by using the slurry from your sharpening stone as a sort of cushion while gently stroking the knife on a medium grit stone. Of course, the condition is that the base be cleanly sharpened.
For the final finishing touches, if you lightly stroke the soft iron with the slurry from your sharpening stone, it will create a beautiful Kasumi finish. Imagine the slurry as a gooey, thick substance. You use the slurry that naturally forms as you sharpen and try to avoid rinsing it off too frequently. This slurry is reserved for the final touch.
However, if it gets too gooey, be cautious – it can create a vacuum-like seal between the stone and the knife, which can be dangerous!
In my rush to capture the above photo, I quickly generated some slurry and sharpened away, but it turned out there wasn’t enough slurry… The sharpening lines are still visible. From this point, if you generate a thicker slurry and sharpen, you can achieve a beautiful Kasumi finish! While a Kasumi finish doesn’t have much to do with sharpness, it’s something for those with a keen eye for detail to try.
By the way, I believe a Kasumi finish may make the knife more prone to rust compared to a mirror finish. Mentioning this might lead some to say, ‘I’d rather have a mirror finish!’ Mirror finishing is even more challenging. It’s a very time-consuming process. Soft iron can become polished depending on the sharpening stone, so take your time and slowly work on it. Rather than just sharpening, think of it as polishing the blade with the stone, and you’ll achieve a knife with a glossy edge just from the stone alone.
The specific sharpening stone can vary depending on the condition of the soft iron in your knife, so I can’t provide a precise product name… If you want that glossy finish, remember that the slurry from your sharpening stone, as mentioned earlier, can cause the Kasumi effect, so be sure to rinse it frequently.
P.S.: Knives made of soft iron that have been hammered and well-tempered tend to shine beautifully. Soft iron can become compacted and harder. The harder it is, the easier it is to achieve that shine, just for your reference!
hibishugyo
- 2010-04-01
