|foundation polishing with pics
||[Dec. 10th, 2011|12:13 am]
Some musings and progress reports under the cut, with some pictures for those who wonder what I"m talking about.|
I have both sides foundation polished to the point that there's no visible oxide from the heat treatment, and I'm working on polishing the bevels down to a sharp edge. The wavey bit polished out with just a bit of edge having to go with it, it's not visibly different from the rest of the wheel, though technically it has to be just a bit out of round now. It's thinnest at the edge there, so I used that to set the angle of the edge bevel -- about 12 degrees. The bevel isn't quite flat, though the convex curvature is going to be pretty subtle.
The edge is thickest opposite where the bend was, rubbing in the lesson that with the forces involved in heat treating these wheels there can't be a weak spot or asymmetry in thickness. To work down the edge, first I used the water cooled grinder to rough in a 45 degree angle until the very edge was only about 1/10th mm all around. I then thinned out a bit of the edge where it was thickest, and shut off the grinder for the last time on this blade.
The Kongo-Do stone is the traditional stone for foundation polishing. Mine is silicon carbide with a clay binder, I'd say about the same as a standard coarse aluminum oxide stone, call it about 220 grit. Plenty coarse for fast removal of material, including as I've found out fingerprints, but with the clay to act as lubricant and to build up as slurry that will abrade without leaving heavy scratches, though I have to prime it with a nagura stone.
Not leaving heavy scratches is hard. These stones take some getting used to. They're soft, so if you're not careful and get your angle wrong, you can deeply scratch them quite quickly. If you dont' use enough water, they clog up; use too much and the clay/abrasive slurry, called mud, washes off, exposing the hard, unyielding grit still attached to the stone and scratching your surface. Some stones generate enough mud on their own that they're fine with just water, others require the use of a chalk-like nagura stone to get and maintain the mud.
It takes an even pressure, constant vigilance on water and mud, and sometimes a reshaping of the stone to achieve the desired effect, and you can feel it when the high resistance of a fresh stone eases as the mud develops, the stickiness when you're on the flat of the blade, the scrape of when it's on the edge, or that desired just-in-between feeling which means you're working things at just the right angle. Back and forth, changing pressure from side to side and back to back to maintain the curve of the edge and the roll of the bevel, trying to cover the entire blade with an even layer of scratches all radiating from hub to edge, and an edge just shy of being truly sharp.
When the stone is broken in, it will have a dip from end to end with a curve matching that of the bevels, but for now I have to do it with hand pressure and a lot of eye checks. This wheel is roughly 2" from hub to edge, much wider than any traditional blade, so the flat stone is less of an issue. It's still not easy, as I mention above I just discovered that I've worn away enough skin to make it quite sensitive on a few fingers. Nothing horrible, but I hate losing hard-earned callus like that. Fortunately there's crazy glue.
My original goal for tonight was one side of a wheel; having been at it and really only gotten a fingerwidth's completed and about 140 degrees started, I'd say maybe I'll get 45 degrees or so before I give up for the night.
In Japan, even the packing material has tentacles. This is the box the stones arrived in.
Kongo-Do, nagura stone, pizza wheel, from top to bottom.
Some historical background and musings below.
There are two sword polishing teaching traditions in Japan; either the apprentice is allowed to progress from stone to stone when he thinks he is finished, or he is only allowed to progress to the next stone when his master thinks that the polish is correct.
Foundation polishing is the first step in sword polishing. Using the coarsest stone, the profile is finalized, the bevels are set, the ridge lines established, and, in short, the blade transitions from a rough piece of heat treated steel to it's final form. All the rest is really just polishing out the scratches left from the foundation stones, to oversimplify hyperbolically.
Both styles of learning have their advantages and disadvantages. If you've spent a few dozen hours on your finer stones, and then discover you have to go back, fix something in the foundation polish, and then redo it all, you rapidly develop an eye for when it's really done, and when you're just wishing it was ready. In my personal experience, I've been disappointed with most of my polishes in the past, and it all comes down to rushing and not doing the foundation polish right, and then not going back and redoing it.
On the other hand, having an experienced master to tell you that yes, you've done it right must be nice -- but I'd imagine very frustrating when you're sent back to the stool and bucket to redo the point for the umpteenth time because it still doesn't match what the old fart is expecting. There are entire books written on different clans and schools and houses of sword polishing and which ones use which technique, and as far as I can tell they both produced great sword polishers. One common thing knifemakers do at hammer-ins is trade knives and ask for an honest critique. I've learned many things about what I'm doing wrong this way, most prominently my unfortunate tropism for the dreaded "clam edge."
Which is a good thing, as I'm kinda lacking the whole "experienced master to tell you when it's right" bit, being an autodidact learning from a large library and a lot of hands-on grinding experience. I'm not trying, yet at least, to follow any given school in terms of design or style, and of course we've lost most of the details of many styles, so all anyone has to go on is what's in the museums, temples, and books. Despite the world's interest in the Japanese blade, in Japan there are few young men interested in carrying on the traditions.
Some Westerners have gone and done the 8 year apprenticeship for forging a blade; polishing, however, takes a 10-year apprenticeship, and there are few willing to give up a decade for that knowledge, so there are far fewer trained polishers than smiths making swords to be polished, and prices have risen accordingly. Current rates for an experienced non-Japanese-trained sword polisher are about $1500 to $2000 for a museum-grade polish, $800 if you're just going to cut with it. If you want one of the formally trained artisans who's considered a master by the judging bodies, well even in Japan they mostly work only on either national treasures or on the work of the living treasure swordmakers.
So, like almost all modern American swordmakers, I do my own polishing. If someone handed me a real nihonto to polish I'd refuse to touch it.
PUBLIC SERVICE ANNOUCEMENT: Should you come into possession of a Japanese style sword which is not clearly of modern mass manufacture, please please please contact the JSSUS (Japanese Sword Society of the United States, jssus.org) before attempting any restoration or long-term storage. It is very hard to tell what is an important blade and what's crap, and even the experts get it it wrong all too often, as several articles on their site point out, resulting in damaged and destroyed swords. I found it fascinating reading, if somewhat overly venomous towards my craft. I would ask them what they think of an amateur polishing the swords he's made, but I can only see a flamewar arising from that given the attitude in their editorials on "amateur sword polishers". /PSA