the sharp corners of a hard slurry stone can dig into the base stone when too much pressure is applied
Printable View
Brooksie
In my book the tomonagura should be just slightly softer than the awasedo base stone. The tipping point is when the tomo will readily and without warning scratch the base stone, this is when it is too hard. But at the same time the tomo should be hard enough to energize the base stone and through simple abrasion encourage the release of some grit from the base stone. This way the beginning slurry mix is a combination of grit/clay particles made up from both the tomo and base stones and the goal is to have a symbiotic perpetual release of base stone grit particles during the slurry finishing stages.
After progressing through the slurry stages, and a rinse of the stone has washed away the slurry, a "slurryless stage" is problematic and can be mis-understood. As I mentioned before the vacuum created between the ultra flat steel bevel and the ultra flat stone during the clear water stages will encourage the release of weakly bound up grit particles, more so and noticable in softer (easier to release grit) stones and less so or noticable in harder stones. But in reality both the soft and hard stones will release some grit because of the suction.
In the ultra hard stones the released rogue grit particle is felt and heard as a single yelp like a dog in the night and this single particle will micro chip the edge of the blade if it reaches the edge (the scratch may lead up to that chip as a pointer). With softer stones used with just clear water the multitude of released rogue particles is deadened as the yelp is echoed amongst the group so that the single sound or scratch is not so visable, but still is present.
The only way I have found to truly water finish a blade without the rogue particles affecting the blade is by honing the water stage under direct running water, like under your kitchen faucet. The continuous stream of running water should be directed so as to carry away any and all rogue particles as they are being released sight unseen.
By carrying out this running water stage I have been able to polish a razor bevel to such a degree that it is scratch free as seen under 800x, and bright enough to resemble the scratch-less finish off my 30,000 grit Shapton. The 30k Shapton gets to that polished place faster than the J-nat, but the sheen is never the less the same.
I am talking bevel here, not edge sharpness. Edge sharpness can be an elusive quality at these ultra high grit levels. Sharp is sharp, no doubt. But for how long is sharp sharp will define and determine if ultra sharp is worth the effort. If you cannot get more then a couple of 5 shaves from a 1 hour honing session well then what's there to brag about.
Alx
Thanks for the info Alx, very helpful indeed.
I've yet to have issues with rogue particules from my Ozuku Mizu Asagi or my Nakayama Maruichi Kiita/Asagi when finishing on water only. Perhaps that is related to the fact that I've only ever finished on JUST water while under the tap.
Talking sharpness again, I've yet to have any issues with edge degredation after any number of shaves. I've got a handful of razors that I've finished on these stones and have yet to have one degrade to the point of needing re-honing. Any razors that have felt TOO sharp have softened up quite nicely.
My recent purchase of a vintage green thuringian has also left me very happy as it is leaving incredibly smooth edges; it is nowhere near as sharp as the edges off of either of my JNATs though.
The difference in hardness between my two stones is, so far, undetectable to me. I've been fooling around with using an extra find dmt card to raise a slurry off the base stone of each for finishing purposes. The Ozuku is a much slower cutter than the Nakayama when using this method. I'm judging that by the length of time it's taking the slurry to change colour.
The Nakayama is also producing a slightly less keen yet smoother edge than the Ozuku. Both stones follow the same trend when finished with diluted slurry.
This is of course, all depending on the razor I'm honing. Some of my razors just don't seem to like the JNAT. Perhaps the steel isn't good enough to handle the edge produced and that's when I finish off my vintage coticule or the green thuri.
Brooksie967
Thanks for the overview and the tie-in with the Thuri. I have also found that under running water the edge can get kicked up a notch or two, and there is little chance of scratching. Keep it up, Alx
Thanks ALX.
Honestly it seems to depend on the razor when finishing on just water. Some razors just don't seem to be able to handle it without getting so sharp that they hurt while shaving, others come off just water incredibly smooth and buttery. At this point if the razors are too crispy I just go back to the jnat and do a few passes with slurry to mellow it out. Still these edges seem much keener than that of my coticule, 12k naniwa, vintage thuri etc.
I've never tried any Jnat under running water, will do tonight!
Got a Daishi 800 Tamahagane that seems to take a really good edge to play with.
The suction thing is not problem only on the Jnats, as Alx pointed, every stone with the above attributes will have this effect. A few ways to avoid it is,
try smiling razors,
use a tiny bit of slurry in the water,
tape,
Or, use the Smiths solution or any non petroleum based liquid with oily feeling that can be washed out easily. Don't worry, you will not ruin your stones.
On the final stages of honing, I always hone under running water. Not only the particles that can get loose, anything that floats in the air can stick on the stone.
Cat hair everywhere!
They also lick my hones and sharpen their claws on them, the Devon Rex goes for the Nakayama kiita and the wild cat for sandstone.
I've found that to be true as well & these days, for touchups & finishing I'm normally just doing 15-20 pigtails followed by 5-10 x-strokes on the slurry. No dilution or water--the edge is super sharp already so why bother?. It feels sharper (beard cutting) & lasts a lot longer that if I went all the way to water. W/ dilution or water, the edge doesn't cut my beard as easily & the razor doesn't hold up for long.
Thanks gentlemen for all the tips. I have a Nakayama Asagi lv 5+ from JNS that was giving me headaches. I lapped it with a 120 dmt as this gives room for the particles and finished on trickle of running water. Under the scope the scratch patterns on what I was doing before and now is that the scratches are shallower. I just shaved with it. You guys are geniuses! Thanks again for sharing the knowledge.
Yes, I've been happily raising slurries on many of my jnats for several years with an atoma 1200. In fact, I originally bought the atoma on the advice of So Yamashita for the sole purpose of raising a slurry on a rather hard jnat. It's always worked well for me.
Having said that I'll often just finish with water and keep going until it evaporates for a couple of dry strokes. Whether you get benefit from that could well depend on the stone though.
James
James
I also learned from So-san about the diamond nagura (DN) years ago, and my worn out Atoma's have tamed many a hard stone. I know that JNS does not recommend using a diamond plate for raising a slurry, it is a great tool and a modern application. Some suggest that using a DN is a waste of good stone. I disagree in that if you use a tomonagura to raise a slurry, it is going to be either the tomo or the base stone that is providing the slurry, and tomonagura are not cheap themselves if they are of the same qualtiy as the base stone.
There are inexpensive tomonagura that might be excellent quality, and those should be picked up whenever possible, ultra quality tomonagura are cut up from ultra quality larger stones. The beauty of the DN is that the slurry is pure base stone particles, it costs no more in dollars or U.K. pounds than the tomo slurry and it matches the base stone perfectly.
It is common to think that a smaller piece of a base stone can be cut and used as a tomonagura for that same base stone, this hardly ever works because one of the two stone being of equal hardness will scratch another leaveing gouges. A DN elimanates this problem. I can assure you that if the diamond plate had been invented 50 years ago some fellows would have used them as DN too. In the really old days though they had access to quality semi-hard stones and super fine grit medium hard stones for razors. Our problem, challange, or gift however you want to look at it now is that so many excellent medium hard stones are so expensive and hard to get and the ultra hard stones are the common goto razor hone. The ultra hard stones can be fine or act as a fine stone too, but they can be ornery. A spanking with a diamond nagura can straighten them up in a hurry.
Alex Gilmore
I find that a much harder tomonagura can work well if your patient enough to prep the tomo. Rounding a corner with a dia plate and using it with light pressure will raise that finer slurry. Or use the dn slurry and break it first with another blade of knife to get it finer before you use the blade your working on. Or use slurry from a prefinisher on your finisher. The work is done on that and the finer finishing stone will max out the edge imo. I think we have to be creative. None of these ideas we have are original.
___________________________________
Maxim sent me a tomonagura to match my Nakayama Maruichi Asagi from old_school. In appearance you would think it was cut from the Maruichi Asagi. The tomonagura makes a slurry identical to slurry made by my DMT 325 credit card and there seems to be no difference in the finished edge from either slurry.
Bill 3152 recently sent me a set of three nagura stones for start-to-finish honing on my j-nats. I will be trying them soon. J-nat honing can be complicated and I keep experimenting.