Polishing progressions - do they really matter?

[ethompson]

Tried searching through the forums for a thread on this, but never found anything that exactly matched what I wanted to discuss.

How much influence do stones used earlier in a progression influence the results of a final polish? Do they at all if you are working clean enough on the final stone to erase all previous scratches? Is it just the final stone that really determines final appearance? Or are the finer details, contrast, etc. only achieved through a careful selection of stones starting at the mid grit stage?

 

[Pie]

I’ve found some stones play better with specific others, although the combinations are endless at this point. I don’t think I’m at the point where I can reaaaally tell the difference between preps.

What stands out to me are certain finishers don’t care - they’ll polish the heck out of any previous step. More often I find suita doing this.

There was one progression that resulted in a black kasumi, but I want to say it was a result of technique on both the prefinisher and the finisher.. I haven’t been able to replicate it using any other 2 stones.

 

[refcast]

Sometimes stones leave a burnish or kasumi finish. . . At the same "grit". When going to the next stone, the kasumi or matte finish on both the steel and iron will poslish faster and with more contrast and detail, whereas the burnished one will be harder to do a little at first. Eventually they will both be the same for me though.

If I don't polish out all the scratches, sometimes I can get a darker kasumi on the iron like I think @Pie tried before.

Now I have had something like what you're asking happen before, but only when I was using the free grit, since the grit is free to go into the harder and softer spots of the steel and iron, exposing their pattern. But stones it's less so. . . Since it's a bit more planar, but stones still show detail

 

[ethompson]

Sometimes stones leave a burnish or kasumi finish. . . At the same "grit". When going to the next stone, the kasumi or matte finish on both the steel and iron will poslish faster and with more contrast and detail, whereas the burnished one will be harder to do a little at first. Eventually they will both be the same for me though.

Yeah I guess that’s what I’m getting at. In the end, does the final stone determine the final finish provided you work it enough to erase previous scratches?

To give a specific example, if you’re finishing on something like a hard and fine Okudo suita or Nakayama Maruka, does it matter if you used a harder or softer pre-polisher? Or used natural midgrits vs synthetic?

Different finishers will leave different results on different knives and finding the right match of knife and stone is an art unto itself, no doubt about that. But to what extent does the stone selection prior to finishing matter for the final outcome?

 

[refcast]

Assuming that the geometry is the same (softer stones tend to dish and make the wide bevel more convex) . . . I mean again, a softer stone is likely going to have more sharp scratches than the burnishing effect of a harder stone. So although the scratch width may be the same between the stones, the scratch shape and surface is different.

The synth vs natural debate is again scratch shape. . . Assuming enough time to completely replace scratches, yeah, the outcome should be the same. Sometimes a harder final stone won't have enough to bite onto on the knife surface and will be slow until some minor roughness is established one way or another (making mud, nagura, diamond plate, using minimal water, etc).

For example, we know some jnats don't give contrast, some do, some give dark kasumi. I assume they were all the same "grit" on the hard steel at least. If I use a hard fine jnat finisher after them, the finisher will cut and make a sufrace texture on the knife differently for each case. . . though after a long period of time, I expect all of the to look the same. But short term, they should all look different. Based on my experiences on messy polishing. . . I guess it also depends on the final stone. If the final stone is a jnat that kind highligh grain and banding, then i think that the previous stone matters more. If its a synth that makes a mirror or default dark kasumi, then I don't think the finish will change too much

 

[cotedupy]

This’ll be an interesting thread I think!

I’m not a particular expert here, but pretty much every stone I have I’ve tried out for polishing, so I’ve probably experienced enough to be able to offer a semi-valid opinion...

Yes, I think it does matter. At least on clad knives, it may matter less on monosteel. Particularly on soft steel the final outcome of a polish does not necessarily just depend on removal of a visible scratch pattern. Particularly because in the case of natural stones, the things that influence it are not entirely dependant on the primary silicate abrasive.

I haven’t done enough proper experimentation with this kind of thing yet to be able to know exactly what I think is happening, or post a load of illuminating pictures. But I’ll say this for certain - I have mid grit stones the use of which (or not) has a greater impact in highlighting banding and layers in a finished result than whatever stone I might use after them.

The other aspect that could well have an impact on stuff like this, and which again I haven’t experimented with much to date, is a stone’s pH.

 

[Blank Blades.]

All that matters is you are setting yourself up for less work in the following step.

After determining the desired end result. I think picking a specific progression is just deciding how to get there with the least work, and most repeatable results.

If your final result is a near mirror kasumi finish from a natural stone. Determining what grit synthetic your naturals can quickly erase the scratches from are the biggest part of deciding the progression. Also knowing if certain stones can leave deep scratches out of nowhere that ruin a finish can make cutting that stone out of a progression make sense. Because it increases the work needed later on.

Tl;dr no it doesn't matter, if you get all the scratches out. Just try to make the work easy for yourself when picking your steps.

 

[ReiHamono]

The final stone is only the final touch

 

[Blank Blades.]

I might try some experiments to see if I can find any kind of definite answer to why people may be seeing different results while polish using different lower grit stones.

The honyaki I've been working with does come to mind when thinking about this, and the effect etching has. The detail brought out by the etch is still visible even after the point where I thought i had gotten any previous surface metal off through polishing. so the answer is, that i must not have actually removed all of it.

What I'm thinking is i can polish something in one area, with a progression taking normal pictures. And also taking pictures with my microscope to show what is really happening.


Like I said. I need to find time before I can do this. Maybe someone remind me in a week or so. In case I forget.

 

[Kawa]

grinding/polishing is very simple.

The final scratch pattern will be the one you see. That can be one gritt, or a blend of previous gritts.
It you remove all the previous scratches, you only see the final stone, whatever that is.
If you don't remove all the previous scratches, you end up with a blend of scratches.

Scratches are mountains and valleys. You can remove all the mountain peaks and create new mountain/valleys (smaller ones for a finer stone), or just flatten the existing (coarse stone) mountain peaks, leaving the deeper (coarser stone) valleys.

It is whatever you desire.


In the world of bowling(balls), we use these effects to finetune the desired reaction in the oil (which is on the lane) through more or less grip.


So, how much do previous stones influence the end results?
That strictly depends if you remove all the scratches of the previous stones.
If you do, previous stones have zero influence (except how fast your progress towards the end result was. But non for looks or performance)
If you don't, youll see the previous stones in the end result.

 

[Martyn]

grinding/polishing is very simple.

The final scratch pattern will be the one you see. That can be one gritt, or a blend of previous gritts.
It you remove all the previous scratches, you only see the final stone, whatever that is.
If you don't remove all the previous scratches, you end up with a blend of scratches.

Scratches are mountains and valleys. You can remove all the mountain peaks and create new mountain/valleys (smaller ones for a finer stone), or just flatten the existing (coarse stone) mountain peaks, leaving the deeper (coarser stone) valleys.

It is whatever you desire.


In the world of bowling(balls), we use these effects to finetune the desired reaction in the oil (which is on the lane) through more or less grip.


So, how much do previous stones influence the end results?
That strictly depends if you remove all the scratches of the previous stones.
If you do, previous stones have zero influence (except how fast your progress towards the end result was. But non for looks or performance)
If you don't, youll see the previous stones in the end result.

I was gonna write something and then saw this.... well this makes my job a lot easier ----

What he said

so yeah, based on my experience, it's only the final one or two stone(s) that really counts, depending on whether the scratches from the (n-1)th stone are completely erased. as far as polishing goes, anything before that doesn't really matter

 

[Martyn]

I was gonna write something and then saw this.... well this makes my job a lot easier ----

What he said

so yeah, based on my experience, it's only the final one or two stone(s) that really counts, depending on whether the scratches from the (n-1)th stone are completely erased. as far as polishing goes, anything before that doesn't really matter

and building on top of that, there is a saying that coarse jnats are useless.

may I take this one step further by saying the majority of "mid grits" are also useless?

full disclosure - it drives me crazy when my knife drags thru food when cutting. so I almost always remove the scratches from the previous stone.

 

[Heckel7302]

and building on top of that, there is a saying that coarse jnats are useless.

may I take this one step further by saying the majority of "mid grits" are also useless?

full disclosure - it drives me crazy when my knife drags thru food when cutting. so I almost always remove the scratches from the previous stone.

You could take it even a step further and say that all jnat bench stones are useless, just end on a synth then rub with finger stones or stone powder to finish. But then what fun would that be?

 

[ethompson]

You could take it even a step further and say that all jnat bench stones are useless, just end on a synth then rub with finger stones or stone powder to finish. But then what fun would that be?

On the other hand, completely erasing even a synthetic 10k scratch pattern with finger stones would require a lot of finger stones... But agree with the sentiment.

Part of the reason I started the thread was wondering if my current mid-grit bender is just a waste of time. I think the answer is that by the time I make it to whatever finishing stone I envision for a given polish, yeah probably. But then I got out my Natsuya and Aizu and realized it was just a lot more enjoyable to me, for irrational romantic reasons, than comparable synthetics.

 

[M1k3]

Just pick one at whatever grit you need that doesn't leave random singular deep scratches.

 

[Blank Blades.]

You could take it even a step further and say that all jnat bench stones are useless, just end on a synth then rub with finger stones or stone powder to finish. But then what fun would that be?

Unless you want a jnat edge.

 

[Martyn]

You could take it even a step further and say that all jnat bench stones are useless, just end on a synth then rub with finger stones or stone powder to finish. But then what fun would that be?

yeah I hear you brother. I have a bunch of mid grits too lol. but the edges off naturals are better. probably should have posted it in the Unpopular Opinions thread

 

[cotedupy]

Scratches are mountains and valleys. You can remove all the mountain peaks and create new mountain/valleys (smaller ones for a finer stone), or just flatten the existing (coarse stone) mountain peaks, leaving the deeper (coarser stone) valleys.

It is whatever you desire

Just pick one at whatever grit you need that doesn't leave random singular deep scratches.

These two points get to the heart of the matter for me. And do so in a more pithy and eloquent way than what I'm about to say...

It is perfectly possible to get a mid grit (say mid 1000s ish) natural stone to leave a finish with no real noticeable scratches to the eye. The point of using a finer stone after isn't to completely erase that finish, it's to build on and refine it. Hopefully keeping aspects of the previous stone's finish, a dark jigane for example, and add nuance from a finer stone maybe to bring some more shine to that, or highlight features of the steel.

There are various reasons that natural stones work better for this in comparison to synthetics. The most obvious being that synthetic stones are meant to abrade; they are designed to be more friable and have constantly exposed new abrasive, and this is particularly important when you consider what they're made from. SiC and AloX are notably harder than silica - synthetic stones inherently cut better, faster and more consistently.

By comparison naturals are harder (less friable) in composition, but the abrasive itself is softer. The slurry on a natural stone doesn't physically 'break down'; what happens is that the silica, which is only marginally harder than hardened steel, rounds out and loses its abrasive power. If the stone is very hard and non-friable you'd call it 'burnishing' the surface, and both mean that the stone becomes slower and the finish shallower as you continue to work it. In this way you're already building a kind of progression when you use a mid grit stone, and it's why even coarser natural stones like Binsui or Natsuya are good in the early stages of polishing. Or indeed for something like setting the bevels on a razor.

A further thing to note is that natural stones often also have other abrasives in them, and depending on the (Mohs) hardness, some of them might have an impact on cladding, but not on core steel. You can't simply view a mid grit stone and a finisher as coarser or finer versions of the same thing, it isn't just about removing or replacing an identical type of finish.

If a natural whetstone is very hard that is usually (not always) the result of lithification. And as well as altering the physical structure of a stone the pressure involved in lithification also compresses and smooths the silica or quartz within it - what might have been circular particles before become disc shaped. Natural stones tend to get cut parallel to the direction of their fissility, or perpendicular to that of lithification, with the result being that the cutting surface is less abrasive and the finish or 'scratch pattern' shallower. Which ties into the other reason you can't view a finishing stone as a finer version of a mid grit, because they're not necessarily. Usually they're just harder...

Very hard and fine jnats *do not necessarily have a smaller grain size*. I have a Maruo Shiro Suita, that is at least as fine as top razor stones under a scope, it's just softer and has had less lithification, so it doesn't finish as fine. The Japanese grading system according to 'hardness' rather than 'fineness' is entirely appropriate for these kinds of stones, and the result of a deep understanding of their of their composition and effect.

---

I realise that the above was slightly rambling, but all of those things impact in various ways to why I think earlier stones in a progression do matter to the finished result. In fact I'd go so far as to say that if you use a finishing stone to completely remove any effect of a previous stone's finish then you're not doing it right.

 

[Blank Blades.]

In fact I'd go so far as to say that if you use a finishing stone to completely remove any effect of a previous stone's finish then you're not doing it right.

Idk if I agree with that part.

Great explanation of everything above that.

 

[cotedupy]

Idk if I agree with that part.

Fair enough (it probably sounded a little bit more didactic than I intended!)

I’m not as expert a polisher as many people here, though I’ve probably tried it off more stones than most. So to put it another way... the best finishes I’ve got, to my eye, include character brought by stones earlier in the progression as well as at the end, rather than just from the final stone.

 

[Blank Blades.]

Fair enough (it probably sounded a little bit more didactic than I intended!)

I’m not as expert a polisher as many people here, though I’ve probably tried it off more stones than most. So to put it another way... the best finishes I’ve got, to my eye, include character brought by stones earlier in the progression as well as at the end, rather than just from the final stone.

That seems like a much more reasonable statement.

To be more specific of what I didn't agree with, it was just the wording, and the absolute nature of it like you said. If you added the caveat, when using japanese natural stones, towards the end off a progression. Then the statement, probably becomes much more accurate.


However I feel like if you apply that to when you're doing the foundational work with synthetics. You really want to be erasing each previous grit completely. Then move up.

 

[cotedupy]

That seems like a much more reasonable statement.

To be more specific of what I didn't agree with, it was just the wording, and the absolute nature of it like you said. If you added the caveat, when using japanese natural stones, towards the end off a progression. Then the statement, probably becomes much more accurate.


However I feel like if you apply that to when you're doing the foundational work with synthetics. You really want to be erasing each previous grit completely. Then move up.

Ah yeah, certainly a fair point. Reading it back - I agree completely, it does sound overly absolute/didactic. TBH I'm never really one to think that the way I do things is any better than anyone else's. And certainly not when it comes to stuff like polishing!

If and when you have the time; it'll be very cool to see the results of a proper experiment, and looking under a microscope. All of my post was just the stuff I know about stones, combined with hunch or impressions I've got from polishing. I've never done any standardised tests or looked at with a scope, so would be very interested to see what's actually going on.

The point about synths is interesting too. And yes - with synths I do tend to really try to erase the previous stone before moving on. Though I only use synths for polishing progressions below 1k really. Even two of my very favourite stones - Cerax 1.5k and Cerax 3k - I don't like for polishing. The scratches are deeper and more random, and they just leave a kinda dark featureless finish apart from that.

Maybe I'm just a hopeless romantic about natural stones though, and trying to justify the not insignificant amount of money I've spent on mid grits! .

 

[Blank Blades.]

Maybe I'm just a hopeless romantic about natural stones though, and trying to justify the not insignificant amount of money I've spent on mid grit natural stones! .

No! Of course not!

Yeah. I might start on that tonight. I only have a couple knives that it might be a good idea to do this experiment on. So I'll pick which one, and go from their.

I'll be polishing only a small section of the blade, just for the sake of saving my time, and also because all my iron clad, carbon steel blades are kind of mid renovation let's say.

 

[Blank Blades.]

Ok picked the knife got started. I get the area up to my 1.2k king. In the picture the lines going in the other direction are from wiping in a different direction. I'll take magnified pictures from here, and do a progression. Taking a normal picture and one under magnified on each new stone. Then I will start experimenting with my jnats in different orders, and with different naguras.

I forgot to add the image last night I guess. Anyway. Here is the king 1.2k. I'll put some more work towards this tonight or tomorrow.

 

[Luftmensch]

But to what extent does the stone selection prior to finishing matter for the final outcome?

I dont think the thread has been explicit about 'the final outcome'. Tacitly; the thread has mostly discussed kasumi finishes but that is only one choice of aesthetic.

Polishing to a mirror can be easy if you have the right buffing wheels and compound. The shine can hide a multitude of sins... particularly at a distance (say arm's length). If you are discerning and look at a 'good-enough' mirror finish closely, you are likely to see evidence of scratches from the final grinding grit. The way light reflects on them will be evident. A perfect mirror finish is much more difficult. You have to spend the time to reduce the grind scratch pattern down to a level that polishing compounds can hide. So even with mirror finishes, the penultimate step can count...

Kasumi finishes can be done with synthetics as much as they can be done with naturals. Technique plays a large role in achieving the outcome you want. Do you want a super dark one? Do you want a bright haze? Do you care if it is 'scratchy'? This can be affected by the slurry (in both synthetics and naturals). Generally.... more mud typically means darker and more water tends to be brighter and scratchier. I have found kasumi to be additive at the low end. If you produce a heavy kasumi at a low grit, the next grit may want to slurry and kasumi faster. Conversely you produce a 'bright' finish at a low grit, you may have to work harder at developing a kasumi and slurry in the next grit (if that is what you want).

I think one of the tricks with kasumi is knowing when to stop. You can polish too much on a high grit and ruin the effects of the base layer. I think what is going on with kasumi finishes, is that light is being scattered randomly in every direction. This is likely why they look 'darker' than other polished parts of the blade... more light is being scattered away from you! The closer you get to a perfect mirror, the more the light bounces directionally. Correspondingly the more directional the reflection, the less 'dark' the kasumi becomes. I don't believe it is possible to get a super dark kasumi and a high, even mirror - it is always some balance between the two. So there will be an interplay between scattering light (usually done at a lower grit) and reflections (done at higher grits). It is up to the end user to decide what their preference is....

Finally... there are also brushed finishes (see here and here). These aren't talked about much on KKF... but you can angst over brushed finishes just like you can with any other finish. The canonical aesthetic is having all the scratches. So long as you remove all scratches running in other orientations, you can achieve a good aesthetic... This means that the previous grit doesnt matter (within reason) so long as it runs in the desired orientation.

 

[cotedupy]

A perfect mirror finish is much more difficult. You have to spend the time to reduce the grind scratch pattern down to a level that polishing compounds can hide. So even with mirror finishes, the penultimate step can count...

I've never really tried this tbh. But on a knife would one not just use a sandpaper progression running as high as possible, and then start buffing and compounding? Stones would seem an unnecessary variable to throw in...

Also - diamond pastes seem very good to me at erasing sanding scratches. I'd have thought that with some time, and various different pastes that a full mirror wouldn't be overly difficult...?

I think one of the tricks with kasumi is knowing when to stop. You can polish too much on a high grit and ruin the effects of the base layer. I think what is going on with kasumi finishes, is that light is being scattered randomly in every direction. This is likely why they look 'darker' than other polished parts of the blade... more light is being scattered away from you! The closer you get to a perfect mirror, the more the light bounces directionally. Correspondingly the more directional the reflection, the less 'dark' the kasumi becomes. I don't believe it is possible to get a super dark kasumi and a high, even mirror - it is always some balance between the two. So there will be an interplay between scattering light (usually done at a lower grit) and reflections (done at higher grits). It is up to the end user to decide what their preference is....

This is a far better explanation than I managed above when trying to explain how I felt about kasumi polishes.

So, for the record... I think what @Luftmensch thinks.



p.s. I remember those pics of your brushed finishes. They were sweet!

 

[Luftmensch]

Also - diamond pastes seem very good to me at erasing sanding scratches. I'd have thought that with some time, and various different pastes that a full mirror wouldn't be overly difficult...?

You're right... I think mirror polishing is pretty simple if you are patient and have the right tools (wheels and buffing compounds). Like I say; you can get a 'good-enough' mirror finish even if you start off with a relatively low grit. At a distance, scratches won't be visible through the shine. Nor when you look at reflections in the polish. Up close and at the right angle, you will see scratches. But they will look different to regular scratches - rounded over and blurred/softer. Just to stay profitable, I would guess this is the approach commercial operators take.

Going the extra distance to ensure you have a good base to start from could be too costly for commercial operators. Perhaps you could get there with a perfect 1000 grit finish and a heavy cutting compound? Maybe you need to start from a 3000 grit? But I bet the temptation is often to jump off a high grit belt sander or grinding wheel. You can see that here and here (be super critical!... and I am not criticising these knives, blacksmiths or vendors!!).

Put another way... you can easily achieve a high surface finish through buffing wheels and compounds. They smooth out the surface... but if you haven't removed deep scratches, your surface will not be locally flat (those small trenches will just be rounded over). A really, really good mirror surface is both smooth and locally flat! But that is more work...

.... perhaps I have unrealistic expectations!!

 

[Kawa]

Perfect mirror doesn't exist.

Even a golden ring at 150.000k has scratches in certain light.
Even a mirror has scraches in certain light, so has glass.

 

[Luftmensch]

Perfect mirror doesn't exist.

Ha! True!

You can often see fine brush marks from the polishing wheel. If you use a very soft wheel and a gentle polishing compound, I am sure even those could be minimised. Still; no over polished 400 grit lines for me thanks!!

 

[cotedupy]

Perfect mirror doesn't exist.

You should meet my friend Mr. Plato... he's got a very good one. Allegedly.