Thread: Natural Stones Approximate Grit

Originally Posted by ppetresen

The trouble with comparing naturals is that even of the same kind there is considerable variance, not to mention that a preferred edge is fairly subjective. A 12k Naniwa should be a standard purchase for anyone getting in to honing since it at least offers a standard reference point to work from.

I agree with this in principle. The problem for me is the default JIS reference that we are assuming on the forums. Only that makes a Naniwa 12k a "standard purchase" as suggested. Or why not refer to microns instead of JIS? Rather, if we go by collective wisdom or word of mouth, we might still arrive an agreed categorical system of "bevel setters," "mid-range stones," "finishers," and the like, be they natural or synthetic. At the very start, I found synth stones too aggressive. So I switched to slower-acting oil-stones like Indias and Arkansas that are difficult to rate as their "grit effect" varies as to polish and simultaneous burnishing effect. And to make matters worse, their grit ratings are given in mesh, or whatever old-school American standard it is, which throws people off. Another complication has to do with natural stones generally being more "fluid" than synthetic stones, with natural stones' effect varying more noticeably relative to added pressure and then lightening up, leading to more of a sliding-scale of perceived JIS grit-rating effect.

Originally Posted by Brontosaurus

The problem for me is the default JIS reference that we are assuming on the forums. Only that makes a Naniwa 12k a "standard purchase" as suggested. Or why not refer to microns instead of JIS? Rather, if we go by collective wisdom or word of mouth, we might still arrive an agreed categorical system of "bevel setters," "mid-range stones," "finishers," and the like, be they natural or synthetic.

Completely agree! I think we could actually pick any number of synthetic finishing hones to use as the reference point, the Naniwa 12k makes sense because of how widely adapted it already is, as well as it's relative accessibility to people. In other words, it makes sense here and now but there is nothing inherent to it that makes it a better choice than a Shapton Glass 16k (for instance).

As long as people are using the same stone, we don't need to give it a grit or micron rating at all, since it would still allow people to say "In comparison to that Naniwa stone, I find the edges off this other stone keener/harsher/softer/duller/etc." This keeps the emphasis firmly on a standard starting point, one that is experiential rather than purely objective. As long as we keep this focus I don't think it matters that we're using the default JIS instead of microns, just that we're more or less using the same stone.

How do you define natural stone? Alumina is AlO2 which is just ground down to a powder. Diamond can be ground to dust and in fact is. The is no limit really with natural stones. When you say "natural" do you mean synthetic versions of these too?

Originally Posted by thebigspendur

How do you define natural stone?

By natural, I consider it formed-as-found in present time by past natural geological processes, extracted from the ground, or as found on the earth's immediate surface in the form of fallen shards, then cut or not cut to size, hopefully lapped flat, and used accordingly.

Originally Posted by ppetresen

Completely agree! I think we could actually pick any number of synthetic finishing hones to use as the reference point, the Naniwa 12k makes sense because of how widely adapted it already is, as well as it's relative accessibility to people. In other words, it makes sense here and now but there is nothing inherent to it that makes it a better choice than a Shapton Glass 16k (for instance).

As long as people are using the same stone, we don't need to give it a grit or micron rating at all, since it would still allow people to say "In comparison to that Naniwa stone, I find the edges off this other stone keener/harsher/softer/duller/etc." This keeps the emphasis firmly on a standard starting point, one that is experiential rather than purely objective. As long as we keep this focus I don't think it matters that we're using the default JIS instead of microns, just that we're more or less using the same stone.

Understood, I hope. I can only differ in that this seems to ignore natural stones as potential references.

A long time ago, someone gave me some advice: a Suehiro 1k/3k synth combo is great for setting things up for naturals afterwards. And in following this advice, I have to say that it has proved true from my experience. No need for any higher synth afterwards, a coticule used with water (no slurry) followed by a purple Welsh slate used with oil almost always suffices, the coticule and the Welsh purple being independent of JIS ratings.

From the perspective of synth progressions in general, it's one that I haven't used much apart from my experience with a Sigma Power 1.2k > 6k> 13k progression a few years past (or after my dabbling with a dedicated Arkansas oil-stone progression). I remember that in starting out with the said sequence, the 13k yielded a harsh or over-honed edge, which I would subsequently calm with a smoothed black hard Arkansas. It was only after continued persistence with the 13k synth as sole finisher that I realized that I was using it with too much standing water on the surface. Rather, it preferred a dampened state with no standing water, from which the end-result regarding the edge was superb. Ergo, even the use and rating of synths seems relative according to the skill, purpose, or circumstance of the user in question.

From this, I would think that certain claims for natural stones used after whatever advanced X-synth stone may be doing much the same. For example, I have never succeeded with shaving off a coticule used after a 3k synth, always needing the Welsh slate afterwards. But if I were to use a coticule to reign-in or tame a harsh edge after a Naniwa 12k, perhaps I might sing the coticule's praises in thinking it was more advanced than the 12k synth.

This topic is really not helping my headache.. I guess if anything is possible, absolute highest could be 50k + but I'd argue the stone wouldn't be homogenous at that size.

I vote 8k for naturals!

A 10k Gokumyo makes a shiny surface by comparison.

Here is a photo of a few stones, a razor, two kamisoris, a piece of 2000 abrasive paper and some oil.

I estimate my natural's grit from looking at the bevels after sharpening, with a high resolution 10x loupe. The surfaces of the bevels all look about the same to me. These are all great finishing stones and the bevels look different from the finish off synthetic stones.

I can not shave directly off any 8k stone (that includes my natural stones). It takes stropping to get a shaving edge for me.

BUT, the action, and effect, of the different stones is significant.

A synthetic 8k stone like a Chosera is very fast cutting. The scratch pattern is regular and the scratch grooves are deep. It also makes a wicked burr which does not come off with stropping, so the shave is nasty.

By contrast, my natural stones grit does not cut as deeply. The grit seems to scrape a wider, thin layer of steel off the surface. The big difference in my experience is that when using slurries with Coticules, Eschers or Jnats, the slurry seems to remove the burr as it sharpens the bevel ... but the slurry also dulls the edge. The final few laps without slurry slowly put a sharp edge on the blade, but the edge still has to be polished on a strop.

My preference is to use Arkansas stones because they are all cutting surface (no mud!) and a few drops of light mineral oil (no stink) work well for me. If I take an edge that has been prepared by a fast cutting synthetic, say 5-8k, the Ark will smooth the bevels and edge, but as there is no slurry, a burr is created too (barely visible, but it glints in the light when looking through my loupe). I remove the burr by wiping a piece of abrasive paper, very lightly, along the edge. In the photo, there is a small piece of 2k paper which I use with a drop of oil. It takes two or three wipes (very light) before the burr is completely removed so that the paper no longer grabs bits of burr. I can feel the difference. Once the burr has been removed, the edge is no longer sharp enough, so I make a few more light laps, maybe ten, to make a new edge which also has a new burr, but it is very small (insignificant).

I then polish the bevels (and edge) with the small stones shown in the photo. They are Gokumyo 10, 15, and 20k. They polish the misty bevels to a high polish quickly, also refining the edge.

This is a good edge to take to a strop. I have made a loom strop (limited sag) which I pasted with 0.25µm cBN. A few light, slow laps on the strop polish the edge to make a fantastic, durable, smooth edge for shaving.

Once I have a good edge, I seldom use a stone again. Stropping keeps the edge for a long time with a good razor. If necessary, a few light strokes on an Ark, followed by the Goks and strop take very little time or effort to restore the edge.

It makes no difference which natural stone I use. None gives me a shaving edge straight from the stone. I am really shaving off the polished edge from the strop.

I have tried some of the vitreous stones, like Jade, Jasper and agate. It looks like they polish the bevels by burnishing, but a leather strop does a better job of polishing the edge for me.

My favorite finishing stones are hard Arks, used with light oil. They are rated at about 1200 grit by Dan's, and I find there is almost no difference between the black, translucent and hard for practical purposes. They are all great.

I enjoy the variety of using other stones. I bought a really nice Jnat, from Alex Gilmore, that feels very nice when lapping. An Escher or Coticule with a thinning slurry is also very satisfying to use. The techniques are slightly different, but they all give me the roughly 8k smooth finish that polishes to a keen edge for the pleasure a smooth, painless shave.

Coticule and Thüringer: 20.000, at least.

For reference, I have shaved with a few Suehiro Gokumyo 20.000 edges, and found they were the same level of sharp and smooth as my coticule and Thüringer edges. Did not last as long, though.

Regards,
Pieter

@Cliveruss.

I'm with ya on the strop.
Something I've added to my stroppin, was to start on a linen strop coated with lead, before going to leather. This is only done, after a honing session, or touch- up.

Lead? What form of lead, and what does it do that plain linen won't do?