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The Saw Mark Fallacy

Now we've all fallen for this in the past, but I'm just going to put it out there in case it saves anyone else any unnecessary both in the future:

Saw marks are easily the stupidest way to try to identify a stone.

The reason is because once stone saws became automated everybody probably used the pretty much the same kind of thing, the reason that saw marks on different stones were different isn't because the saws were different. Here are six stones, all cut by the same person, on the same machine, on the same day (I saw him saw them with mine own eyes):

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Admittedly you can have more than one saw blade on a machine, but that's neither here nor there, these stones were all cut with the same blade. The reason the marks are different depends on other things: How much you raise or lower the blade, which will depend on the depth of the stone. How fast you put the stone through it, which will depend on the person using it and what they think the stone can take in terms of softness/hardness. And how many passes you do, which will also depend on the person doing it, and what they think about the depth. It could all just depend on how hungover someone is on a particular day.

As you can see; even on the same type of stone, cut by the same person, with the same machine - the number of variables above, particularly human variables, can produce wildly different outcomes.

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Now obviously there is a well-known exception to this, some Thuringian stones were cut with a particular type of saw (I assume non-automated), and have quite distinctive saw marks. But not all Thuris have these, some have other saw marks, and some might have been lapped through. So all it'll tell you is if you definitely do have a Thuri, not having them doesn't necessarily mean that you don't. It won't give a false positive, but it can give a false negative.

Apart from that though... trying to id a European stone from saw marks is a fool's errand. You might as well be reading tea leaves.

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And lastly, as you perhaps guessed from the sentence above, I don't know about whether this holds for Japanese stones. I know you can sometimes tell stuff about their age from saw marks, but perhaps different mines did use different saws too? Can one of our jnat experts (@Steve56 @rideon66 @alex1921 &c.) offer any insights here...?
 
Now we've all fallen for this in the past, but I'm just going to put it out there in case it saves anyone else any unnecessary both in the future:

Saw marks are easily the stupidest way to try to identify a stone.

The reason is because once stone saws became automated everybody probably used the pretty much the same kind of thing, the reason that saw marks on different stones were different isn't because the saws were different. Here are six stones, all cut by the same person, on the same machine, on the same day (I saw him saw them with mine own eyes):

View attachment 1597621

View attachment 1597622


Admittedly you can have more than one saw blade on a machine, but that's neither here nor there, these stones were all cut with the same blade. The reason the marks are different depends on other things: How much you raise or lower the blade, which will depend on the depth of the stone. How fast you put the stone through it, which will depend on the person using it and what they think the stone can take in terms of softness/hardness. And how many passes you do, which will also depend on the person doing it, and what they think about the depth. It could all just depend on how hungover someone is on a particular day.

As you can see; even on the same type of stone, cut by the same person, with the same machine - the number of variables above, particularly human variables, can produce wildly different outcomes.

---

Now obviously there is a well-known exception to this, some Thuringian stones were cut with a particular type of saw (I assume non-automated), and have quite distinctive saw marks. But not all Thuris have these, some have other saw marks, and some might have been lapped through. So all it'll tell you is if you definitely do have a Thuri, not having them doesn't necessarily mean that you don't. It won't give a false positive, but it can give a false negative.

Apart from that though... trying to id a European stone from saw marks is a fool's errand. You might as well be reading tea leaves.

---

And lastly, as you perhaps guessed from the sentence above, I don't know about whether this holds for Japanese stones. I know you can sometimes tell stuff about their age from saw marks, but perhaps different mines did use different saws too? Can one of our jnat experts (@Steve56 @rideon66 @alex1921 &c.) offer any insights here...?
The only JNAT saw marks we usually speak of for age are not actually just saw marks and it just has more to do with being hand done and not powered. It just says it was around 1920s or earlier nothing else really. So the hand saw marks we speak of are actually sawn then scraped with something like a ski-sen. It is a tool that is also used to scrap out the hollow on the ura of kamisori if it gets too flat.
 

David

B&B’s Champion Corn Shucker
I’ll (mostly) disagree. Yes, you can’t solely go by saw marks as an identifier, but they are a strong indicator in ID’ing unknown stones. For example, if I come across an unlabeled stone that’s 7x1-5/8 and 13/16 thick, I immediately suspect thuri, but we all know there were other random slates cut that size, so I look at saw marks. There’s three types of saw marks you will see on thuris, which I’ll have to post pics of when I get home, but you have the primary saw marks, the secondary grind marks, and a third that’s hard to explain in words. If I see any of those I assume Thuri and confirm with a shave test.

Another example is SSOFGR’s. How many unlabeled special stones have you seen? Tons, and yet one glance at the saw marks and you know what it is. There’s nothing else like it.

As Tom mentioned the hand sawn marks on jnats are very unique, but I’ll add that most of the legit Maruka stones that I’ve seen have the same saw marks, and that many of the bogus Marukas look like you had them sawed by a teenager working in the lowes tile department. And with jnats it’s not only saw marks that can be an indicator of when the stone was mined but also tool marks commonly found on the back of the stone.

That’s my two pennies, Galileo.
 

Steve56

Ask me about shaving naked!
JNats are maybe a little different. Saw marks changed over time because saws and sawing them changed over time. Early on, they were hand sawed, from one side then the other to keep the surfaces from flaking out, then they were smoothed with a sen, or scraper. These are old stones, early 20th century or older.

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I’ll (mostly) disagree. Yes, you can’t solely go by saw marks as an identifier, but they are a strong indicator in ID’ing unknown stones. For example, if I come across an unlabeled stone that’s 7x1-5/8 and 13/16 thick, I immediately suspect thuri, but we all know there were other random slates cut that size, so I look at saw marks. There’s three types of saw marks you will see on thuris, which I’ll have to post pics of when I get home, but you have the primary saw marks, the secondary grind marks, and a third that’s hard to explain in words. If I see any of those I assume Thuri and confirm with a shave test.

Another example is SSOFGR’s. How many unlabeled special stones have you seen? Tons, and yet one glance at the saw marks and you know what it is. There’s nothing else like it.

As Tom mentioned the hand sawn marks on jnats are very unique, but I’ll add that most of the legit Maruka stones that I’ve seen have the same saw marks, and that many of the bogus Marukas look like you had them sawed by a teenager working in the lowes tile department. And with jnats it’s not only saw marks that can be an indicator of when the stone was mined but also tool marks commonly found on the back of the stone.

That’s my two pennies, Galileo.


And a fine tu’pence it was! But I don’t think you’re really disagreeing with me...

There may be one or two* stones where particular saw marks could give you a positive id, but not a negative one. And there are a thousand other types of stone where it’s a complete red herring.

I just wouldn’t call that a ‘strong’ indicator. ‘Overwhelmingly futile’ might be closer... ;)


* I don’t think I’ve ever had a SSOFGR, so didn’t know that about them tbh.
 
It's still pretty useful with Thuris... mainly because of how the stone itself takes scars mixed with the ability to somewhat date (due to cutting methods/tools)... and most Thuri fakes being modern and most same-era thuri "lookalikes" being french (Very distinct sawmarks from Germans) or UK (Usually quite shallow/cleaned up saw marks).


edit:
That and most of the frauds selling Welsh slates and Mueller Slates as vintage Eschers haven't learned/tried very hard to replicate sawmarks. I think the guys doing the modern La Lunes may have tried to replicate the vintage chamfers and sawmarks (Did they? Seem to recall some pictures looking like it)... but at least their label is distinct enough that if you're educated/aware of the modern repro Lunes existence they're only potentially a threat of faking to guys who will remove the label and try to pass them off as vintage... which given the price vs vintage price... doesn't make sense (yet). That's more of a thing to worry about in the future if the vintages take an uptick in value for some reason.
 
For the sake of a good discussion, name five.


I showed you six in the OP! Admittedly only four different types, so in addition to the Penryhyn Grey, Ruby, Dragon’s Tongue, and Cwt y Bugail, I shall add: Water of Ayr. Five.

(Though the list is almost infinite, I assure you...)
 
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David

B&B’s Champion Corn Shucker
I showed you six in the OP! Admittedly only four different types, but to the Penryhyn Grey, Ruby, Dragon’s Tongue, and Cwt y Bugail, I shall add: Water of Ayr. Five.

(Though the list is almost infinite, I assure you...)
Lol. I’ve only heard of two of those so can’t really comment on them.

Pretty much the only time saw marks are ever brought up around here are for thuris, jnats, and Lunes or special stones, and in that group of stones they are very helpful for making an ID.
 

Steve56

Ask me about shaving naked!
It’s supposed to be a SSOFGR. Those are the ends, the sides have been smoothed (the side had a stamp). The back of mine is also lapped for use, the way that I got it.
 
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