The Kasumi finish
When sharpening Kasumi knives, I’m always thinking about how to create the Kasumi finish. Normally, using a 1000-grit medium whetstone will produce the Kasumi effect, but the challenge lies in making the Kasumi finish on the curved tip.
When you try to maintain the curve while sharpening, you inevitably end up with sharpening marks (or should I say sharpening lines?) like those shown in the photo.
Note: The white lines on this photo have been added afterward.
Why do these lines appear? When sharpening a knife, you use a flat whetstone to work on the curve. When you focus on maintaining the curve, the flat surface of the whetstone gets interrupted by the curve, resulting in these step-like sharpening marks that appear as lines.
However, if you want to remove these lines and create a smooth Kasumi finish, there’s a way to do it. By using the slurry from the whetstone as a cushion and gently sharpening with a medium grit whetstone, you can eliminate the lines. Of course, this assumes that the primary bevel is properly sharpened.
For the final “cosmetic sharpening,” gently polish the soft iron part with the slurry from the whetstone to achieve a beautiful Kasumi finish. The slurry should be thick and pasty, produced from extensive sharpening. Instead of frequently washing it away, use it for the final touch.
Be cautious, though: if the slurry becomes too thick, it can create a vacuum between the whetstone and the knife, which can be dangerous. Adjust the consistency carefully to get the best results.
In my rush to take the above photo, I quickly created a slurry and started sharpening, but there wasn’t enough slurry yet. You can still see the sharpening marks in the photo. From this state, if you continue to sharpen with a thicker, more viscous slurry, you can achieve a beautiful Kasumi finish!
While the Kasumi finish doesn’t greatly affect the cutting performance, it’s worth trying for those who appreciate the aesthetic. However, be aware that a Kasumi finish can make the knife more prone to rust.
For those who prefer a mirror finish instead of Kasumi, it’s a much more challenging and time-consuming task. Depending on the whetstone, even the soft iron can become shiny, so by carefully ‘polishing’ rather than just ‘sharpening,’ you can achieve a glossy blade using only whetstones. The exact whetstone depends on the state of the soft iron, so I can’t specify a particular product.
When aiming for a glossy finish, slurry can cause a Kasumi effect, so be sure to frequently wash it away.
P.S.: Knives that have been hammered and thoroughly hardened (soft iron) tend to shine better. The more compressed and hardened the soft iron, the easier it is to achieve a shiny finish. Keep this in mind!
- 2010-04-01
