A while back I asked Matt and Bob what a hamon was in this post:

Hamon Comment by Bob Katilus

Apparently he thought it important to let me know that he just returned from Florida while your favorite Web geek remained in New York slaving away on his site….

Yeah, back from sunny Myrtle Beach, and I am already grinding metal.

Jim, the geekhood title is a good thing; Matt and I wish we were at the geekhood level (I know, I shouldn’t be speaking for Matt). Actually, even “geek apprentice” for us would be a step up.

The hamon is the visual manifestation of the knife’s spirit. If you touch it, you can feel the coldness of the spirit running through it (unfortunately, only Matt will understand the joke). Really, the hamon shows the hardness line, as the knife was differentially heat treated. Clay is placed on the spine when quenched, so that the edge hardens and the spine remains somewhat “soft”, which will allow some flex without snaping the blade. When acid etched, the acid “eats” the steel at different speeds when the hardness is different. And most importantly, it looks PRETTY COOL!!!