Opinions on sword

[cabowen]

There has been a lot of research over the years, both in English and in Japanese. C.S. Smith was an early Western investigator. There have been others....

 

I did some hardness testing while an engineering student; I only had a few specimens but my results were in line with the literature.

 

In general, the final hardness depends on how much carbon was present at the steel during the quench, the speed of the quench, and the time and temperature of the tempering. The time and temperature of the tempering determines who much hardness is drawn from the blade....There is the often heard opinion that koto blades are softer than shinto, and that shinshinto and later are much harder. That doesn't mean they weren't tempered, it may mean they were harder (more carbon) to begin with. Tempering does more than lower the hardness, it also relieves stresses. It is an important step in the smithing process.

[runagmc]

It would be interesting to see how tempering affects levels of nie, brightness of nioi-guchi, and other activities. You'd have to polish the blade before tempering and then again after. I wonder if this has ever been done.