Knife sharpener?
Forget grit numbers. Grit is conceptual, not absolute.
For starters, if an Ark is lapped and surfaced well, it's not equal to any 1k synthetic. In an excel sheet way you can read the quartz grains as being about 1400 grit or so, but particle size discussions don't apply when it comes to Arks due to how they are formed.
I have owned enough black Arks to ballast a schooner, none of them would compare favorably to a 1k Naniwa Chosera, or similar, when it comes to bevel setting a razor.
Try to understand that grit ratings for synthetic stones are not based on an actual particle size.
The current most popular method of enumerating 'grit' comes by way of comparing any given particle's volume to a virtual spherical model with that volume.
Imagine a rhombic/square particle, lets say its dimensions factor to a volume of 1/10000 cc.
Then take a perfect round and smooth particle that also contains 1/10000 cc of volume.
Will both particles abrade steel the same way?
No, they don't. But they have the same grit.
This is one reason why the JIS standard actually has two scales, one for that method and one for a type of sifting method. The number vary wildly sometimes. You never who measured what which way. Then binder types and particle density in that binder get factored in.
8k in JIS system can be read is approx 2 microns but it's not stand alone, particle size along with particle density matter.
Binder type creates different cutting action too.
Different synth manufacturers have their own spin on grits, it's usually relative within their product lines, often not exactly comparable to other makers.
Chromox for finishing razors could be rated 30k, or more typically 50k, but maybe numerically 60k. Most stuff used by razors guys is .5 µm. Chromox for the auto industry can be a mix of things and all over the place in grit values and polishing action. Dovo used to sell a green paste that was much coarser, 6 µm I think. You have to know what you are using, exactly, to know what 'grit' it is supposed to be. So if your green compound is 6k then following with 8k isn't out of the question. Probably not needed though. Depends on things not visible in this discussion.
Jnats do not have grit.
Assigning grit to coticules is also pointless. The abrasives in those stones are not at all comparable to synthetic stones.
Arks are rated by density. A black ark can be pretty soft or ultra hard, more density = the possibility of greater refinement capability. Just because the possibility is there, doesn't mean you automatically get it though. Variables matter. Skills and technique matter more. It's not add water and stir. I used to finish, refine edges, on Coticules after honing to 12k on Naniwa stones. Yes, using slurry. So not 6k/8k. If used differently, incorrectly, without exploiting their capability, things might appear differently.
Lastly, mirror polish doesn't equal 'good edge'.
More mirror doesn't equal 'better edge'.
The more magnification you use, the more scratches you will see. Even a Level 5 mirror polish is built on scratches and if you use enough magnification you will see them. Polishing steel is scratching steel.
FWIW, I don't shave with the bevel. The apex of the edge is what does the work and apex condition should never be assumed to as being identical to the condition of the side of the bevel.
Razors with hazy and messy looking bevels can deliver some of the best shaving edges out there. All of my edges are hazy but some have more 'mirror' to them than others.
I don't know why a bevel would have a grey stripe. I used to see that on razors honed on Norton combo stones but, for example, my bevels aren't striped. Typically, the 'look' is uniform from shinogi to apex.
I know sometimes people are obsessed with higher grades of mirror polish for some reason, and that can be achieved with using abrasive compounds in the .25µm and .1 µm realm.
Anyone looking to learn how to hone edges that shave better, regardless of appearance might consider learning to set the bevel well enough so a shave can be managed with it. Contrary to the expert advice spewed endlessly around shavng platforms, it isn't hard to do and once achieved the world is one's oyster.
The bevel is the edge, without a 100% bevel, anything done afterwards is just polishing a turd.
I'd recommend getting a good bevel setter and learning it. Me, personally, I would not want to use any black Ark for that work, 1k-ish synths of good quality are worth their weight in gold. Can the Ark be used? Sure, I guess. I just don't see the point in starting with a hurdle or trying to swim upstream for no good reason.
Flattening the stones so they are actually flat when checked with a straight edge can help.
Removing inconsistencies and variables from the equation helps a lot.
Forget grit numbers. Grit is conceptual, not absolute.
For starters, if an Ark is lapped and surfaced well, it's not equal to any 1k synthetic. In an excel sheet way you can read the quartz grains as being about 1400 grit or so, but particle size discussions don't apply when it comes to Arks due to how they are formed.
I have owned enough black Arks to ballast a schooner, none of them would compare favorably to a 1k Naniwa Chosera, or similar, when it comes to bevel setting a razor.
Try to understand that grit ratings for synthetic stones are not based on an actual particle size.
The current most popular method of enumerating 'grit' comes by way of comparing any given particle's volume to a virtual spherical model with that volume.
Imagine a rhombic/square particle, lets say its dimensions factor to a volume of 1/10000 cc.
Then take a perfect round and smooth particle that also contains 1/10000 cc of volume.
Will both particles abrade steel the same way?
No, they don't. But they have the same grit.
This is one reason why the JIS standard actually has two scales, one for that method and one for a type of sifting method. The number vary wildly sometimes. You never who measured what which way. Then binder types and particle density in that binder get factored in.
8k in JIS system can be read is approx 2 microns but it's not stand alone, particle size along with particle density matter.
Binder type creates different cutting action too.
Different synth manufacturers have their own spin on grits, it's usually relative within their product lines, often not exactly comparable to other makers.
Chromox for finishing razors could be rated 30k, or more typically 50k, but maybe numerically 60k. Most stuff used by razors guys is .5 µm. Chromox for the auto industry can be a mix of things and all over the place in grit values and polishing action. Dovo used to sell a green paste that was much coarser, 6 µm I think. You have to know what you are using, exactly, to know what 'grit' it is supposed to be. So if your green compound is 6k then following with 8k isn't out of the question. Probably not needed though. Depends on things not visible in this discussion.
Jnats do not have grit.
Assigning grit to coticules is also pointless. The abrasives in those stones are not at all comparable to synthetic stones.
Arks are rated by density. A black ark can be pretty soft or ultra hard, more density = the possibility of greater refinement capability. Just because the possibility is there, doesn't mean you automatically get it though. Variables matter. Skills and technique matter more. It's not add water and stir. I used to finish, refine edges, on Coticules after honing to 12k on Naniwa stones. Yes, using slurry. So not 6k/8k. If used differently, incorrectly, without exploiting their capability, things might appear differently.
Lastly, mirror polish doesn't equal 'good edge'.
More mirror doesn't equal 'better edge'.
The more magnification you use, the more scratches you will see. Even a Level 5 mirror polish is built on scratches and if you use enough magnification you will see them. Polishing steel is scratching steel.
FWIW, I don't shave with the bevel. The apex of the edge is what does the work and apex condition should never be assumed to as being identical to the condition of the side of the bevel.
Razors with hazy and messy looking bevels can deliver some of the best shaving edges out there. All of my edges are hazy but some have more 'mirror' to them than others.
I don't know why a bevel would have a grey stripe. I used to see that on razors honed on Norton combo stones but, for example, my bevels aren't striped. Typically, the 'look' is uniform from shinogi to apex.
I know sometimes people are obsessed with higher grades of mirror polish for some reason, and that can be achieved with using abrasive compounds in the .25µm and .1 µm realm.
Anyone looking to learn how to hone edges that shave better, regardless of appearance might consider learning to set the bevel well enough so a shave can be managed with it. Contrary to the expert advice spewed endlessly around shavng platforms, it isn't hard to do and once achieved the world is one's oyster.
The bevel is the edge, without a 100% bevel, anything done afterwards is just polishing a turd.
I'd recommend getting a good bevel setter and learning it. Me, personally, I would not want to use any black Ark for that work, 1k-ish synths of good quality are worth their weight in gold. Can the Ark be used? Sure, I guess. I just don't see the point in starting with a hurdle or trying to swim upstream for no good reason.
Flattening the stones so they are actually flat when checked with a straight edge can help.
Removing inconsistencies and variables from the equation helps a lot.
But ain't it the truth.....
