So I've been struggling with a Japanese blog post for a bit, but the gist of it seems to be this:

This guy took an old kitchen knife, dunked it in a mild (pH 5) acid solution and pumped oxygen and electricity through it for an hour and a half. It resulted in lots of black pitting, like we call devil's spit. Interestingly, the acid solution was made from natural hone slurry...one with a high level of sulfur

Then, he took the other end of the knife, put it in a stronger acid solution (pH 3.5--made by adding vinegar to the previous solution) and did the same.

This time, it resulted in cloudy kasumi effect, which under magnification showed tons of tiny little specks of that black rust. IN fact, it looked identical to the finish from a high end natural stone.

Now, one of the more "legendary" effects of a Japanese finisher is that it actually hardens the edge; someone actually tested an edge and said that it bumped up the rockwell by 2-3 points. I myself have always been skeptical. However, this guy speculates that perhaps, as I have seen myself, some stones are chemically prone to promote oxidation, and since Iron Oxide is harder than the Iron element of a blade, it can lead to hardening as it hones.

I'm not at all sure of the science, but it seems an interesting idea.

For those who can read Japanese, or like to look at pretty pictures of steel, here's a link to the blog: Å·Á³ÅÖÀФβâÌÏÍ͡ʺ½ÌÏÍ͡ˤòºÆ¸¡¾Ú - ÍïÇÀ²È¤Î¥Ö¥í¥° - Yahoo!¥Ö¥í¥°

So...what do you think? Anything meaningful or interesting here? I must admit, the idea is intriguing. If there is any reality to the "natural stones hardening steel" thing, it would be pretty cool.