Solor stick sword for sharing & comment

[Roland_M]

Originally Posted by Timo Nieminen

"Low-tech" is not the same as "unskilled" or "low quality". I have seen low-tech metalwork of superb quality. Low-tech just means that the smith doesn't have power tools (e.g., power hammers), temperature controlled ovens for tempering, access to steel of known composition, quantitatively accurate hardness testers, etc.

Yes, differential hardening with a clay coating is more difficult than uniform quenching. I don't think this blade would have been done that way - probably edge-quenched instead.]

The difficulty in low-tech heat treatment isn't the quench. As you say, you can tell temperature of very hot steel by colour. The tricky part is tempering to reduce the brittleness after quenching. This will be even more the case if the blade is wootz (or some other very high carbon crucible steel); tricky enough so that wootz blades were often air-cooled rather than quenched.

Differential hardening, whether by differential quenching, differential tempering, or laminated/composite constructions like welded-edge/inserted-edge or sanmei add a lot of forgiveness to the heat-treatment process, especially tempering.

Interesting thoughts, thank you.

Yes much of the old tempering technique got lost. For example, many modern researchers laughing about the fact, that old blacksmiths were using prayers and religious songs during their work, because they don't know, that this was a kind of stopwatch for perfect timing.

In my opinion this blade is clay tempered, otherwise it would not have such a clear and bright hamon.

[Timo Nieminen]

I don't think you can tell by the contrast how the differential hardening was done. Width of the hardened region, and pattern - especially fancy patterns - can give you clues.

Also length of blade. It's harder to do an edge quench on very long blades.

But, in the end, if the smith knows what he's doing, differential hardening with a full quench with clay coating (AKA clay tempering, even though it isn't tempering) isn't that difficult. Compared to a full quench without clay, you need more materials and more knowledge, but not that much more. And it makes tempering more forgiving, so the overall heat treatment can be more reliable.

For an interesting example, see
http://www.gunsite.co.za/forums/show...se-style-hamon
which shows some blades done with a combination of edge quench and clay coating. The dips and rises in the hamon have the same contrast - the dips are due to the clay, the tops of the rises are due to the edge quench.

Hamon from edge quench in wax:
http://edgematters.uk/thread/3117-blades-with-hamon/
A solid quench medium can make it easier to do edge quenching on curved blades. I have heard of fruit being used (traditionally).

[Sajen]

Hello Roland and Timo,

thank you both for your explanations!