Sharpening Double Bevel Knives
1. Preparing
Knife - The knife you are going to sharpen. Wash it to ensure there is no excess dirt on the surface.
Whetstone - Whetstones that need to be soaked in water should be soaked in advance. If you are unsure, soak the whetstone in water; if many bubbles come out, it is an absorbent whetstone, and you should soak it until almost no bubbles appear. We used this combination stone for this demonstration.
Whetstone Holder - This is a holder to prevent the whetstone from slipping. If you don't have a whetstone holder, place a damp cloth or similar under the whetstone to prevent slipping. The whetstone holder used in the photo is here.
Cloth/Towel - You may need to wipe the moisture off the knife several times to check the sharpening status, so it's a good idea to have a cloth ready.
Newspaper - Used to remove fine burrs at the very end.
2. Flattening the Whetstone Surface
The most important thing when sharpening is that the whetstone is not loading and that the surface is flat. Before sharpening, always correct the surface to make it flat. There are various types of flattening stones; the better ones produce a more accurate flat surface and flatten the stone faster. A diamond plate is used in the photo, but there are various other flattening stones available. Drawing a cross-hatch pattern in pencil across the entire surface of the whetstone before flattening the surface will show you if the surface is truly flat. Always flatten the surface before or after sharpening.
3. Sharpening the Front Side
Please maintain a small amount of water on the whetstone at all times, as shown in the photo (above). If the water evaporates while sharpening, take some water in your hand and add it little by little.
When holding the knife with the edge facing down, the right side is called the Omote (front/face) and the left side is called the Ura (back/reverse). If the knife is not particularly thick or chipped, start sharpening with a medium whetstone, which is generally around #1000 grit.
Hold the knife with your dominant hand and sharpen the front side at a 45-degree angle to the whetstone, applying 70% of the force when pushing and 30% when pulling.
At this time, the blade angle should be about 15-20 degrees; for a Santoku knife, you can use the gap equivalent to two coins between spine and stone as a guide. If the angle is too low, the edge will be weak, and if it is too high, the sharpness will not improve.
Use the entire surface of the whetstone, sharpening with a feeling of sliding the knife rather than pressing it down.
4. Creating the Burr
Once one side is sharpened and becomes acute, the ground steel curls over to the opposite side; this is called burr. Continue sharpening uniformly until this burr appears across the entire edge.
(If you look closely at the photo, you can see the top of the edge blade sparkling; this is the burr. If you gently slide your finger from the spine toward the edge, you should feel a slight roughness. The burr in the photo has been slightly exaggerated.)
5. Sharpening the Back Side
Once the burr is uniformly present on the front side, sharpen the back side. Sharpen this side the same way as the front, but at a 90-degree angle to the whetstone. Ensure the burr appears across the entire edge on this side as well. At this time, do not focus only on spots where the burr hasn't appeared or parts that are easy to sharpen; sharpen the entire edge uniformly until the burr is present everywhere.
6. Removing the Burr
Once the burr is uniformly present on the back side as well, you will begin to remove the burr. Place the side with the burr (in this case, the front side) against the whetstone and slide the knife over the stone the same way as before, using almost no force. By repeating this process, alternating between the front and back sides, you will notice the burr gradually disappearing. Be careful not to apply force, as this will sharpen the knife again and recreate the burr.
7. Sharpening with a Finishing Whetstone
After confirming that the burr has been mostly removed, proceed to use a finishing whetstone, which is typically between #3000 and #6000 grit. Since the grit of this stone is finer, it creates a finer edge, resulting in a knife that cuts well and stays sharp longer. Use this stone to remove any remaining burr that the medium stone could not eliminate.
The motion is the same as with the medium whetstone, but finish without applying force, ensuring you do not create a new burr. As you sharpen the front and back sides alternately, you will notice the edge becoming shinier than it was with the medium stone.
8. Removing Micro Burrs
Once finished sharpening, slide the blade across newspaper, a cloth, or denim to remove tiny burrs that could not be removed by the whetstone. Touch the blade by sliding your finger from the spine toward the edge, confirming that the rough burr is gone. If a large burr remains at this point, you may need to go back to the finishing whetstone to completely remove it
9. Testing the Edge
Try cutting a small twisted piece of tissue or kitchen paper. If it cuts better than before sharpening, it should cut food well too.
Finally
This explanation assumes the user is a right-handed person; left-handed individuals should generally reverse the instructions.
If your knife quickly becomes dull even after sharpening, you should consider the quality of your knife or the hardness of your cutting board. If your knife is made of a steel that is too soft, or if your cutting board is too hard, the edge will quickly dull. If it dulls quickly even with good equipment, it is often because the sharpening angle is too low or the burr has not been completely removed. Sharpening is like driving; even if it feels difficult at first, you will gradually get used to it and become good at it. The satisfaction of cooking with a sharp knife you sharpened yourself is invaluable. Please be careful not to injure yourself and take your time with the challenge.