mas4t0

Thank you Shannon. I'm more than happy to defer to your superior knowledge on any points of disagreement. There has been testing (of sorts) carried out in dojo, if we want to compare swords in their (current) practical application. I think at this point there's plenty of empirical evidence (in the field) of (contemporary) traditional blades bending (much) more readily than mono-steel blades. This has been my experience as a practitioner and I'm sure others can attest to this too. Tameshigiri tends not to do any more harm to the blade than bending it out of shape. I'm surprised the hear that XRF is considered accurate to 5 decimal places. Is that 5 decimal places of a percentage (as in 0.1 ppm)? I should maybe clarify that my meaning above with "perfectly forged" was very loose (which is to say, misleading and incorrect). My meaning was "free of weld flaws" as opposed to "the grain flow is oriented to optimise ductility, toughness, strength and fatigue resistance." I didn't mean to make apples and oranges comparisons between forging and stock removal. What I meant to state is that it doesn't matter whether you remove material via a milling machine or by hand and that it doesn't matter whether you (hot) forge an object by hand, with a power hammer, with a press, etc (all else being equal).

Hi Dan, I have a sukashi tsuba mounted on the sword I use for Iaido, it's never caused any problems.

Juan, Please give me your word that you'll never play Three-card Monte. 🤣 I fear that we're now approaching the subjects of Media Studies (e.g. Hyperreality) and Media Literacy . If you didn't see something with your own eyes, it's media and should be viewed sceptically. You know this of course, I'm just defining things as I go for clarity . Even if we saw it with our own eyes we can easily be deceived (e.g. magic tricks). In general I wouldn't trust any scientific findings unless they're from a well controlled study, with a large sample size, replication studies, etc and the field on the whole has reached consensus on the correct interpretation of the findings; hence my strong affinity for textbooks (though always the most up to date editions). I'm fortunate to not be a research scientist, so I don't need to stay up to date with journals. To elaborate a little of what was stated previously; when steel is fully melted you can easily remove dissolved and chemically bonded impurities. How far you want to go with this is a matter of how much you want to spend; you can (for instance) remelt the material under a vacuum (or inert gas) to improve alloy qualities (refined microstructure, further purification, etc). There are a couple of commercially available variants of 52100 which are produced this way, but I don't know if any knife makers are using this steel instead of "standard" 52100 (52100 is quite popular among knife makers in the US). Regarding Howard specifically... He's under-promising and over-delivering (which is ideal). He has no need to self-promote as the word of mouth promotion he receives from his customers has and will always give enough work keep him busy. Most of his customers are practitioners, so the performance is tested. Unreasonable expectations and the bad word of mouth that would follow could ruin a smith. Ordering a blade from Howard really means that you can specify all aspects of the sword based on what would be optimal for you in an iaito; the blade will perform exceptionally well as a shinken without giving any special consideration to how well it'll hold up. If I were using a Nihonto, I'd most likely need to use a blade a few inches shorter or a fair bit heavier to ensure that it wouldn't bend. It also gives me the confidence to let others use it without worry. Bending plastically (i.e. taking a set) in Nihonto is not ideal; it would be much better if it bent elastically (i e. if it returned to its original shape without the need to apply further external force). Plastic deformation is better than breaking, but it's not without adverse consequences. If you take a bank card and bend it back and forth a few times, it'll break. The same idea applies to a sword, you just get more cycles.

I can see why you'd think that, but it's not quite the case. As simply as possible; the ideal structure for a piece of steel is complete homogeneity (lamination is a different topic). This is most easily achieved by fully melting the steel in a "ladle". With the steel entirely liquid it can be stirred to ensure an even distribution of all alloying elements (homogenisation) and liquid chemistry techniques can be used to remove Oxygen, degass, add alloying elements, remove inclusions, remove Sulphur, etc. High grade (premium) steels, which are characterised by narrow chemical tolerances and high consistency, are only possible to produce in bulk due to this process. The history of a material (i.e. processing) influences its structure, and thus the material's properties and performance. Forge welding steel is kind of like taking a dozen small ice cubes, melting the water on the surface and sticking them together to form a single big block of ice. You know intuitively of course that the block of ice would be stronger and less prone to separation if it had formed as one large crystal (i.e. if all the liquid water had frozen together into a single large block). The same idea applies to a piece of steel, which should ideally consist of a single crystal. The negative effects of this can be minimised (maybe eliminated), but even when the steel is worked perfectly, the resulting steel would only be equally good (mechanically) to mill steel (of the same chemical composition) and not better than it. Metallic crystals are not perfect. Often there are empty spaces called "vacancies", where an atom is missing. Another common defect in metals are dislocations, which are lines of defective bonding. These and other imperfections, as well as the existence of grains and grain boundaries, determine many of the mechanical properties of metals. When a stress is applied to a metal, dislocations are generated and move, allowing the metal to deform. The numbers given on the data sheet are based on mill steel. Any alternative approach to producing the same alloy (not involving fully liquidating the steel) will produce at best an equivalent piece of steel and often an inferior piece of steel (from a mechanical perspective), for the reasons explained above. It does not matter whether the (pre-forged) mill steel is forged or is shaped by stock removal. It does not matter if the steel is ground by hand on stones, with a grinder or is machined on a CNC machine. It does not matter if the steel is forged by hand, with a power hammer or by any other means. All that matters is whether or not the piece of steel was damaged by the processing. The same science applies in both cases, it's just a case of how close you're getting to the "ideal" and how much skill and labor are required to get there. The atoms neither know nor care whether they are being forged or ground by hand or by machine processes. The precision of a good blacksmith is close to CNC machining and in many cases will exceed it (for certain items). Skilled smiths can do things by hand which cannot be achieved by machine processes. There's no reason to think of them as fundamentally different. Its like expecting the nutritional content of a cucumber to be different if its sliced by a food processor as opposed to a knife.

Hi Juan, I'm not trying to prove anything, everything I'm saying has already been proven. This isn't Basic Research, it's Applied Science. This is all about mathematics and engineering (with a little materials science and metallurgy). With that in mind I should probably bow out of this discussion, as I won't be able to explain this in a way that makes things clear. I'll try like this... The underlying theory has been very well established. Experiments still take place (to establish mechanical properties) with very well controlled, standardised methodology. If you want to know the theory and the relevant experiments, you'll want to collect a few textbooks in the aforementioned subject areas rather than looking in journals. The contents of those textbooks would be pre-requisite knowledge to really understand the content of the journals of those subjects. To properly understand would require quite a lot of study. With Mechanical Properties (e.g. toughness, strength), Geometrical Properties (e.g. second moment of area) and a grasp of Mechanics, you can understand all of this without the need for destructive testing of swords (as highly controlled destructive testing is already being carried out on geometrically identical samples). I explained the testing methodology for toughness. Other mechanical properties have similarly rigidly defined standardised testing protocols. The bulk mechanical properties of various alloys (having undergone specific heat treatments) will give you a clear understanding of how swords made of those materials will respond to the same abuse relative to one another (all else being equal), without needing a destructive test each time. The best way to assess the difference made by steel and heat treat is to compare them directly, not to add a number of confounding variables. If you are set on destructive testing of swords, your best option would be to buy a traditionally made shinken and commission an utsushi from Howard, build a testing apparatus and document the results of your destructive tests. Otherwise you'll never get to the bottom of this if you want to use an experimental approach. If you don't do it, I don't imagine anyone else will ever fund this. The problem with a testing methodology which allows other (uncontrolled) variables is that it's easy to optimise for the test (if there is incentive to do so). You remember the emissions scandal? Cheating those kinds of tests is very easy when you have control over enough variables. This is the same way. It's easy to tweak the design of a sword to "cheat" the testing methodology (whatever the methodology is) so long as you know the methodology ahead of time and have freedom with regard to a few variables. This is what happens with the ABS Master Bladesmith tests. The knives they make for the test wouldn't be great in real world use because every aspect is optimised to pass the tests (at the expense of real world practicality). We have plenty of evidence to know that it's certainly every time Howard's HT is used and the blade doesn't fail during the HT. The causality is very clear and obvious. Regarding Chinese blades (which nobody else has been discussing)... Howard gives his blades an edge at 57-58 HRc (Martensite) and a body around 48-50 HRc (Bainite). It would be easy enough to test the hardness of one of the Chinese swords. Checking the microstructure would be more involved and would require a professional to prep the surface and interpret what they see under the microscope. If edge rolling is common in Chinese production blades, I would suspect that they're Bainite at the edge (as opposed to Howard's Martensite edge) and that the edge is softer. Why destroy a $5k blade, what would the incentive be? Would you be inclined to spend a week sweating in a forge to craft something by hand and then destroy it for no good reason? Be sure to share those videos if you find any. Is the whole field of Fracture Mechanics not enough for you? This is kind of like arguing that you have no reason to believe that a car with no wheel bearings or tyres would be more fuel efficient with wheel bearings and tyres (and requiring an academic paper for each individual car to verify this). Think about this: If you know with certainty and mathematical precision that: Adam can bench-press 100kg. Brian is 3x stronger than Adam (in every lift). Charles is half as strong as Brian (in every lift). How much can Charles bench-press? Do you need to go down to the gym and find out experimentally or is there perhaps a simpler way to arrive at an answer?

There's a huge amount of other factors at play. What has happened previously? Was the metal already fatigued? How heavy was the niku? What was the cutting edge angle? What was the diameter of the iron rod? What was the chemical composition of the iron rod? What was the magnitude of the momentum and kinetic energy transferred upon impact? There are far too many variables to compare blades in a meaningful way (especially from videos and written accounts). It's far more worthwhile to compare the materials.

Juan, No, there is not a video destructive testing a sword Howard would be willing to sell to a customer, why would you expect this? The video was made with a dead blade which was unsuitable for sale. In the full video the issues with the blade prior to destructive testing are fully detailed, along with the motivation behind the testing. I like it this way as (1) it sets a low water mark (i.e. you know with certainty that if you buy an L6 blade from Howard it will outperform the blade in the video) and (2) he didn't destroy a perfectly good sword. By all means share any journal articles which you think are relevant, but this is hardly cutting edge stuff. What I've been laying out so far on this topic is very basic information you'd find in a textbook and in data sheets rather than in contemporary journals. I'm not sure which parts you want journal references for (the journals would be antiqued) or what you think they would help with. Are you wanting a journal article about Howard's blades specifically?! If so I'm not sure which journal would feel it worthwhile to publish such an article. I concur with John's answer but if you want something more technical I can elaborate further. If so, let me know your background and I'll try to adjust the answer accordingly; I have a tendency to give overly technical answers which irritate more than inform people. Your clue here is that the comparison is being drawn to structural steels as opposed to tool steels. Most structural steels are optimised for low cost (as a lot of material is used). Very few structural steels are quenched and tempered, A514 is one example and it's use is generally restricted to applications where very high strength is required in order to save weight. Structural steels are hardly the gold standard for high performance. As I recall, tool steels are broadly speaking >5x the price per tonne of structural steels. You can review the data sheets of the various alloys to better understand their properties. The historical destructive tests are not consistent (even when conducted with the same methodology), but the data sheets for the various alloys will tell you all you need to know.

The differences are quantifiable and it's not really about the smith. With modern mill steel, the sword-maker only really needs to worry about the geometry of the blade and the heat treat (which can be very accurately controlled with thermometers, salt baths, etc). If you take a piece of mill steel and shape a blade on a belt grinder (stock removal), you'll have a perfectly forged blade (as the blank is pre-forged); so you can now make excellent swords (though of course not Nihonto) without being a smith. It's also maybe worth noting that the blade used in the video above by Howard was defective. If memory serves correctly it had failed during heat treat. The comparison is a little more involved to do properly, due to the laminated construction of Nihonto, but perfectly forged tamehagane (i.e. perfectly homogenised and with no forging flaws) is significantly lower in toughness than L6 at the relevant hardness levels. (I don't have a reference to hand for this). It's also worth noting that perfectly forged was not the norm for Nihonto, but is the norm for mill steel (unless the smith folds, pattern welds or does something very silly with the steel). Toughness is the ability of a material to absorb energy and plastically deform without fracturing. Toughness is the strength with which the material opposes rupture. No Nihonto can perform as well under destructive testing as one of Howard's L6 blades (with identical geometry), due to the differences in material properties. Fracture toughness testing is rigorous in a way that old school testing modalities were not. The process is as follows: Machining of a standard test specimen (typically a single edge-notched bend or compact tension specimen), which is notched in the area of interest. Growth of a fatigue precrack by application of cyclic loading, usually at room temperature. Attachment of displacement measuring gauges across the crack mouth Maintenance of a stable specimen test temperature, typically the minimum service temperature of the component of interest Application of a monotonically increasing load, whilst monitoring both load and crack mouth opening. Breaking open of the specimen to allow detailed measurement of the crack front (occasionally, this happens during the test itself). Calculation of the relevant toughness parameters. Validation of the results. As the toughness of the material determines the toughness of the sword (for a given geometry), we can compare the materials directly. There was a thread recently where a member had a bohi carved in his (traditionally made) shinken, and consequently the blade was bending very easily. If the sword were made from L6, the additional strength would have prevented this.

Thank you Dirk.

The spreading of Ag2S is clearly due to the lower density. The density of Ag2S is 7.23 g/cm³ The density of Silver is 10.49 g/cm³ So Ag2S will occupy ~50% more volume (per gram) than the unreacted Silver (and as discussed ad nauseam, there's more mass in the reacted Ag2S on account of the added Sulphur). Presumably the expansion would occur evenly in all (unobstructed) directions, similar to thermal expansion. I can't really envisage it spreading sideways without an accompanying growth in height, as it's not a fluid (which would tend to flow and be "flattened" under its own weight due to gravity). I'd expect more of a "mushrooming". 🍄 Is there something else going on here that I'm missing? Has anyone seen this in practice; does the Ag2S grow vertically (i.e. at a normal to the surface) in addition to spreading sideways (i.e parallel to the surface)?

Thank you Glen for catching that typo, I apologise if I caused anyone any confusion. I'll stick with chemical formula from now on! Regarding solubility of Ag2S, I was answering (what I understood as) a very specific question: whether silver would be lost from a mass of silver if an electrolysis reaction were used to reduce Ag2S to Ag in the absence of any mechanical separation. This reaction is often claimed to not lose any silver in the process; I disagree. The core of my argument was that if nothing else, some infinitesimally small amount would be dissolved into the solution. Do you disagree with this? I realise the solubility is very, very low. At 6.21e−15 g/l you'd get around 1 metric ton of Ag2S dissolved in the Atlantic Ocean. I maybe wasn't clear, I simply meant to state that it's not entirely insoluble. My guess in the above posts was ~1000 atoms in 1 litre of water. The mass of Ag2S which would dissolve in 1 litre of water = 6.21e−15g The molar mass of Ag2S = ~248g The number of moles of Ag2S which would dissolve in 1 litre of water is: 6.21e−15g/ 248g = 2.5e-17 2.5e-17 * 6.02e23 = 15,050,000 molecules of Ag2S dissolved in 1 litre of water, which means (unless I've made an error) 30,100,000 atoms of silver in that 1 litre. Meaning my guess before could be as much as 30,000x too low. While the solubility is low enough to classify Ag2S as insoluble, it is not truly 100% insoluble (in the binary sense). This is also of course assuming pure water. It would probably be more clear to write this in terms of Mass (the quantity of matter in a physical body) rather than Weight (the force acting on the object due to gravity). Conceptually, "mass" (measured in kilograms) refers to an intrinsic property of an object, whereas "weight" (measured in newtons) measures an object's resistance to deviating from its current course of free fall, which can be influenced by the nearby gravitational field. I would say something like: "The mass (i.e. the quantity of matter) of a physical body (i.e. a collection of matter within a defined contiguous boundary in three-dimensional space) will increase if additional matter is bound to it and decrease if matter is removed from it." Or maybe even more simply: "If a physical body has a net gain of matter, the mass (i.e. the quantity of matter) will increase and vice versa." The key concepts are matter and mass and from there, there's not really much more you say; the above is like saying, "If I get more stuff, I'll have more stuff." It doesn't seem worthwhile to say because the definitions themselves are doing the heavy lifting, but that's all we're really saying in the general sense and it works for all scales from the very small (e.g. sub-atomic particles) to the very large (e.g. galaxies). On a macro scale, if you amputate and eat a chicken's leg (bones and all), you will have gained mass and the chicken will have lost an equal amount of mass. If the chicken eats your leg, you will have lost mass and the chicken will have gained an equal amount of mass. This is of course all zero sum overall.

Maybe this will be of interest too: this is about the best we can get (in terms of durability) with contemporary metallurgy while still having a true hamon.

My mistake; what I meant to say is: "The atomic nucleus of a stable isotope will not (ever) decay spontaneously." This is by definition. Some "stable" isotopes (i.e. no radioactivity has been observed for them) are predicted to have extremely long half-lives; over 1 quintillion (1,000,000,000,000,000,000) years. However, if any radioactivity is observed (i.e. if it can be detected experimentally at any point) those isotopes will be re-classified as radioactive. I think you're describing Cosmic Ray Spallation, but (on earth) it only occurs in the uppermost few meters of earth's atmosphere. Cosmic rays cause spallation when a ray particle (e.g. a proton) impacts with matter, including other cosmic rays. The result of the collision is the expulsion of particles (protons, neutrons, and alpha particles) from the object hit. These neutrons can then interact with other nuclei, as in the formation of (radioactive) Carbon-14 which is continually formed by the interaction of neutrons with (stable) Nitrogen-14. Note though that the radioactivity comes about from the transformation of the stable nuclide to a radioactive nuclide, which will then decay in accordance with its half-life. The strong force binds the nucleus together, while the weak force is responsible for radioactive decay and an important participant in nuclear fission and fusion. Regarding covalent Vs ionic bonding... If the compound were truly covalent (with identical electronegativities) all the oxidation states would be zero, as in the case of diamond where the bonding is between only carbon atoms. By convention all shared electrons are assigned to the more electronegative nuclei (for the sake of oxidation state), but this is clearly not the case in practice (especially where the electronegativity is very similar).

The tarnish is Silver Sulphide (Ag2S), it is reacted Silver on the surface and not a layer of dirt. I presume the reaction you're describing is: 3 Ag2S + 2 Al → 6 Ag + Al2S3 It's an electrochemical reaction, making use of Aluminium's greater affinity for Sulphur than Silver's. By "bringing the electrons back into the silver" you are reducing the Ag2S to Ag. Although the ion exchange would presumably be taking place at the surface of both metals, Silver Sulphate is very slightly soluble in aqueous solution (i.e. where water is the solvent) so there would be some losses into the solution. The solubility is listed as 6.21e−15 g/L (25 °C), so the losses would be extremely small, but they would not be zero.

Your scales would not be accurate and precise enough to measure the loss of mass, but if you remove the patina you have removed material and as such the mass would now likely be in the range of 0.99999999999999999999 oz as opposed to the original 1 oz. Prior to removal of the patina (assuming you have exactly 1 oz of Silver), the total mass may be in the region is 1.0000000000001 oz on account of the extra Sulphur you've you've collected on the surface. Silver has an atomic mass of 107.8682 u. Avogadro's Constant tells us that there are 6.02214076 × 10^23 atoms per mole. 1 oz is ~28g. 1 mole of Silver would weigh ~108g 1 oz of Silver is ~0.26 moles (28g/108g) So your 1oz of Silver contains ~1.56 x 10^23 atoms (0.26 * 6.02214076 × 10^23). Thats: ~156000000000000000000000 atoms. I'd guess that after removing the patina, you might be down to 155999999999999999999000 atoms. That would be a loss of 1000 atoms. You'd never pick it up on a scale, and the atoms would still exist (you wouldn't have annihilated them), but you would have forever removed them from the object you'd removed the patina from. I don't know what's contentious here. This is elementary Physics and Chemistry which have been very well understood for a long time. If you want a practical example of this, consider Silver plating: The plating is typically 10 to 25 microns thick. The lattice constant of Silver is 0.409 nm (think of this as the length of one side of the cube occupied by a single atom of Silver). So a 10 micron plating of Silver would be ~24,500 atoms thick (10e3 / 0.409) and a 25 micron plating would be ~60,000 (25e3 / 0.409) atoms thick. These platings wear through quite readily and there's tens of thousands of atoms. The mass of the object would change but the losses would be so slight that you wouldn't detect them with a scale; you would however see the loss of material as the copper beneath was exposed. I've never taken a piece of silver plated material, left it to patinate, removed the patina and then repeated the process until the plating is gone, but I assure you that the plating would be lost this way over a long enough span of time.

Aqua Regia does not only change the state of matter, the Gold is oxidised and has undergone a chemical reaction. The Gold can easily be reduced to return to pure Gold, but this is more than a change of state. A state change refers classically to solid, liquid, gas, and plasma. This is not a state change (i.e. melting the Gold to turn solid Gold into a liquid), but is a chemical reaction involving Oxidation of Gold; just as rust is formed through the Oxidation of Iron. In a chemical reaction none of the matter is used up (that would be a nuclear reaction). If we consider complete combustion of Methane: Methane + Oxygen → Carbon Dioxide + Water But this does not tell the whole story and could give rise to misunderstandings regarding conservation of mass (i.e. an assumption that mass is not conserved when in fact it is). The Stoichiometric equation which is properly balanced accounts for conservation of mass by including the ratios of the respective reactants and products: CH4 + 2O2 → CO2 + 2H2O Since: 1 mole methane = 12 +4 =16g 2 mole oxygen = 2×32 = 64g 1 mole CO2 = 12 + 32 =44 g 2 mole water=2 × 18 =36g From the balanced reaction: 1 mole(or 1 molecule or 16 g) of CH4 reacts with 2 moles (or 2 molecules or 64 g) of oxygen to give 1 mole (or 1 molecule or 44 g) of CO2 and 2 moles (or 2 molecules or 36 g) of water. For the gaseous system at STP (Standard temperature and pressure): 22.4l methane reacts with 44.8l of oxygen to give 22.4l of CO2 and 44.8l of water. No mass is gained or lost. No nucleus can be "destroyed" other than by radioactive decay, fission, fusion or potentially annihilation; this is true of every element and is in no way specific to Gold and Silver. Conservation of mass is a fundamental premise of all Chemistry and is in no way unique to Gold and Silver; I don't understand where this misconception is coming from.

Chris, Gold and Silver are not meaningfully different to other atomic nuclei from the perspective of particle physics. Nickel and all subsequent (i.e. higher atomic number) elements were formed via Supernova Nucleosynthesis (or perhaps in the core of Neutron Stars). The atomic nucleus of a stable element will not (ever) decay. Gold and Silver are no different from any other stable element in this regard. There are however unstable isotopes; Gold-198 for instance is a radioactive isotope of Gold which undergoes beta decay to stable Mercury-198 with a half-life of 2.697 days. Additionally, Gold can be Oxidised and fully dissolved in Aqua Regia; Gold can be Oxidised. No atomic nucleus is altered in any chemical reaction; the nuclei are only alerted in radioactive decay, fission and fusion. Chemical reactions only affect chemical bonds and the energy released or absorbed in the reaction is dependent on the difference in enthalpy of the bonds broken and the bonds formed. "When the universe is long gone", whatever that means, it would surely presuppose that the matter and energy would be long gone (including Gold and Silver). From a chemical perspective, oxidation of iron is fully reversible. This is what smelting is all about; extracting a metal from its ore via reduction, but this doesn't help much with regards to an object as the corrosion is permanent and the iron is now elsewhere. Oxidation is, technically speaking, loss of electrons. An atom (or atom group) loses electrons when it is oxidised - conversely, an atom or atom group that gains such electrons is reduced. In inorganic nomenclature, the oxidation state is represented by a Roman numeral placed after the element name inside the parenthesis or as a superscript after the element symbol, e.g. Iron(III) oxide. Combination of both half-reactions is what is termed as a Redox reaction, an electron transfer from one chemical species to another. Gold “does not oxidise” according to our experience because it ranks very high in the so-called electrochemical series (Standard electrode potential), a list of how easy it is to oxidise chemical species. As Gold is above oxygen (the commonest oxidiser), no oxidation occurs to it. However, the reaction with Aqua Regia does involve Oxidation of Gold to form Chloroauric acid (HAuCl₄) in solution via the following reaction: Au + HNO₃ + 4HCl ⟶ [AuCl₄]¯ + [H₃O]⁺ + NO + H₂O

To return to this point of agility Vs inertia and how easily people lose their lives when sharp/ pointy weapons are involved; there's a video circulating social media of an altercation (in a food court in Australia) where one man (holding a knife) swings at another man and makes contact with his neck... The man noticed the blood streaming from his neck, collapsed on the floor, and died very shortly thereafter. It's a horrible thing to see. I won't share the video here, for obvious reasons. It really is important that (if possible) people get a little bit of experience in boxing, kickboxing, etc and learn a proper guard. If you do have to face someone armed with a sharp weapon, you'll probably get stabbed and cut either way, but a solid guard and some training will at least ensure you properly protect the neck and have some chance of survival. This felt worthwhile to mention, but please delete if it's too far off topic.

I realise I'm a few years late; I didn't see this until earlier today. Attached is Jussi's document, reformatted as a spreadsheet. Miekkojen hintaseuranta NMB version 1.xlsx

My personal opinion is that while papers in theory wouldn't be granted in this situation (certain exceptions aside), low level papers shouldn't be taken as a guarantee of condition. Which is to say; I'm sure there will be a few blades which slip through when they really shouldn't. There's also of course the possibly of damage to the blade after papers were issued.

I hadn't ever given it any thought, but when writing the above (with consideration of soft kitchen knives and the need for honing to align the edge) I realised that the hardness of Japanese swords is the reason why we don't need to re-align the edge when cutting. I wonder if the (historical) scarcity of leather in Japan maybe contributed to the demand for and development of swords which did not require stropping to maintain the edge? To keep this post on topic, the edge staying aligned and not needing honing is the opposite of "losing the edge easily". A link with photos to clarify what I'm talking about: https://scienceofsharp.com/2018/08/22/what-does-steeling-do-part-1/ Here if you want to get deep into sharp (expect Scanning Electron Microscope (SEM) images of blade edges at 20,000x magnification): https://scienceofsharp.com/home/ As an aside, which may be of some interest. I have several kitchen knives made from Hitachi Shirogami Steel, which is designed to be chemically similar to the edge steel of Nihonto (though Shirogami is completely homogeneous mono-steel). The steel sharpens very easily and takes an extremely fine edge, in fact I'd wager that I can get a keener edge with Shirogami than any other steel. Shirogami doesn't hold its edge as well as Aogami (which has additional Tungsten and Chromium) but Shirogami gets sharper and is both easier and faster to sharpen. A video comparing Aogami (blue) and Shirogami (white):

Many of the terms used by Jean are terms of art, which may not be fully understood by everyone reading without some further clarification. I wrote a bit (hidden below), but it was growing too long so I thought it better to find some sources to link to. Brittleness Brittle and Ductile Materials Ranking Toughness of Forging Knife Steels

Even if someone hasn't had the opportunity to handle a lot of swords, they'll likely have a decent intuitive grasp of dynamics from the use of racquets, bats, hammers, axes, etc. So let's imagine a continuum with a badminton racquet at the left and a hammer at the right. Further left gives greater manoeuvrability, speed and agility due to lower tip inertia (inertia referring to an object's resistance to change in motion). The low inertia of the head of the badminton racquet and the shuttlecock (weighing ~5g) results in measured speeds of the shuttlecock (in competition) of just under 500 km/h. Further right gives increased tip inertia so it'll cut more effectively but at the expense of manoeuvrability (as a direct consequence of the higher inertia). Basically it'll tend to continue along the path it is following, even when acted on by an external force (whether that be from the opponent's flesh or force applied at the hilt), meaning that it requires more force to change it's motion i.e. that a given force will result in a lower rate of change of velocity (i.e. lower acceleration) due to the greater mass (Force = Mass * Acceleration). You'd have just as little success driving a nail with a badminton racquet as you would playing badminton with a hammer. On our continuum, the rapier is (quite significantly) to the left of the katana just as the épée and sabre are to the shinai. Note that the shinai is lighter than the épéé but that the higher tip inertia requires (facilitates) an entirely different style of swordsmanship. The video below is perhaps of interest. It's worth keeping in mind though that a shinai is significantly lighter than a katana (so is faster, more manoeuvrable, etc) while the épéé is slightly heavier than the smallsword on which it's based (so the smallsword would be faster, more manoeuvrable, etc). These are all trade-offs in the design of the sword and, with a sharp weapon, I'd generally prioritise agility. Blunt force is very different. It's often a good strategy in boxing (for instance) to take two or more glancing blows in order to land one solid blow in return. Julio César Chávez vs. Meldrick Taylor (17 March 1990) is possibly the best example of this. Size and weight make a huge difference in blunt force, in fact one of best boxers of our generation recently lost in a big upset after moving up one too many weight classes and facing an opponent who was too big and strong for the difference in skill to carry the day. Sharp and pointy things change that entirely, in the absence of armour you only need to touch the opponent to end his life. In a duel I'd rather have the agility to cut first than have the tip inertia to cut deeper. All of that said, I'd always want a Japanese sword if duels, fights, etc were to begin with blades sheathed as opposed to blades drawn. A swordsman skilled in Iai will have killed his opponent with a draw cut before the opponent (armed with a smallsword for instance) has even begun to draw his blade. Hi Michael, Those are from an online tool called the Weapon Dynamics Computer. There's not much documentation provided: Documenting Sword Dynamics Walkthrough The tool facilitates quantifying the key variables for comparison of different swords. It's especially useful when you already have a frame of reference and want to understand the dynamics of blades you can't handle in person. This video gives a practical demonstration of the fundamental aspects of sword dynamics: If you ever have some spare time on your hands and want to get to grips with dynamics more generally I'd suggest this course. Dynamics is a knowledge world in and of itself so it probably can't be understood much beyond what we've covered here without running though the underlying physics. Sword dynamics is a quite simple application of dynamics, so I'm not sure if there exists any book specifically on the application to swords. If you watch this course though you'll be able to apply it to anything you want.

Given that what I said above is very qualitative and that you'd really need to handle some different swords to understand the difference, I'll add some diagrams. Diagrams will be more useful than diving into physics and the associated technical terms; radius of Gyration, Mass at blade node, Hilt Inertia, Tip Rotational Inertia, etc. Here's the effective mass curves and agility diagrams of a few very different swords. Below is the effective mass curve and agility diagram for a katana. There will of course be quite significant variation from one specific blade to another, but in my experience this quite well shows the handling characteristics of a katana as compared to the other sword types shown above. As you can no doubt intuit from these diagrams, the katana will much more easily amputate arms or cut a man in two but is much less nimble. Clearly it's not just about mass (how heavy the sword is). Imagine lifting a bar loaded with 80kg, now imagine if all 80kg were loaded on one side of the bar... With the above in mind, the following videos should clarify the way the dynamics of the blade affect swordsmanship. Katana: Longsword: Épée (770g 90cm blade): Sabre (500g 88cm blade): Shinai (~500g ~80cm):

Yes, of course, a Japanese sword will work just fine to murder an unarmed man. It'll work just fine even if you have no training, so long as you draw the blade successfully. That said though, a large shard of broken glass will work just fine for that purpose. However, you'd very likely lose a duel against an (equally skilled) opponent using any of a large variety of European sword types; though it would serve you much, much better than the aforementioned meat cleaver. The point being made here isn't on the basis of metallurgy, but on the basis of the different dynamics, handling characteristics, range, etc and the very different fighting styles which the swords lend themselves to. The question raised at the start of the thread is a very high level question, which is to say that it can't be answered succinctly. The most appropriate response really is to provide a list of a few books which lay out the foundation for the discussion, but I'm guessing you're not sufficiently invested in this to read 1000+ pages? On the point of quality, it depends how you define it. If quality (to your friend) means durability then he'll no doubt agree that overalls are higher quality than bespoke suits.