The dents create air pockets so food does not stick to the blade.
In his story, How To Make a Sushi Knife, in the August 2015 BLADE®, ABS master smith Wally Hayes explained how he achieved the texturing on the blade’s surface. The reason for the texturing is to create air pockets so food does not stick to the steel.
For blade material, he used 90-thousandths-inch-thick 15N20 carbon steel from New Jersey Steel Baron.
After cutting the blade to shape and heating it in his forge, the author used the hammer with a cross-hatched face to give each side of the blade a textured finish.
“First, I cut the blade to shape, around 7 inches long,” he wrote. “The tang is about 4 inches. I take one of my old hammers and cut a cross hatch into the face using a side grinder with a cut-off wheel. Then I heat up the blade in my forge and hammer a textured finish into the steel. This takes about five heats and is lots of fun! I put dents into both sides of the blade and then make sure it is straight.”
The sushi knife the author completed for the story in the August 2015 BLADE® features a blade with the hand-hammered finish and a handle of ebony and walnut.