Collections: Iron, How Did They Make It, Part III: Hammer-time

This week, we continue our four-part (I, II, III, IV) look at pre-modern iron and steel production. Last week we took our ore and smelted it into a rough, spongy mass of iron called a bloom; this week we’re going to go through the processes to reshape that bloom first into a consolidated billet, then into a bar that is useful for forging and finally into some useful final object.

I want to stress at the outset that we are not going to cover anything close to the whole of blacksmithing practice in this post. Blacksmithing is fairly complex and any given object, shape or tool is going to have its own set of processes and techniques to produce the required shape at the required hardness and malleability characteristics. If you are interested in that sort of information, I recommend A.W. Bealer’s The Art of Blacksmithing (1969) as a fairly good starting point, though there is no substitute to speaking with a practicing blacksmith.

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Heat, Hammers and Hardness

There are a few basic behaviors of iron that fundamentally control what blacksmiths are going to do with it in this stage. To begin with, we need to introduce some terminology to avoid this coming confusing: a given piece of metal can be hard (resistant to deformation) or soft; they can also be ductile (able to deform significantly before breaking) or brittle (likely to break without deformation). This is easiest to understand at the extremes: a soft, brittle material (like a thin wooden dowel) takes very little energy and breaks immediately without behind, while a hard, ductile material (the same dowel, made of spring-steel) bends more easily under stress but resists breaking. But it is also possible to hard hard brittle materials (pottery being a classic example) which fiercely resist deforming but break catastrophically the moment they exceed their tolerances or a soft, ductile material (think wet-noodle) which bends very easily.

(I should note that all of these factors are, in fact, very complex – far more complex than we are going to discuss. In particular, as I understand it, some of what I am using ‘hardness’ to describe also falls under the related category of yield strength. Hopefully you will all pardon the necessary simplification; if it makes you feel any better, ancient blacksmiths didn’t understand how any of this worked either, only that it worked.)

Of course these treats are not binaries but a spectrum. Materials have a degree of hardness or ductility; as we’ll see, these are not quite opposed, but changing one does change the other – increasing hardness often reduces ductility.

The sort of things that pre-modern people are going to want to be made in iron are going to have fairly tight tolerances for these sorts of things. Objects that had wide tolerances (that is, things which could be weak or a little bendy or didn’t have to take much force) got made out of other cheaper, easier materials like ceramics, stone or wood; metals were really only used for things that had to be both strong and relatively light for precisely the reasons we’ve seen: they were too expensive for anything else. That means that a blacksmith doesn’t merely need to bring the metal to the right shape but also to the right characteristics. Some tools would need to finish up being quite hard (like the tip of a pick, or the edge of a blade), while others needed to be able to bend to absorb strain (like the core of a blade or the back of a saw).

Keep all of that in mind as we discuss:

Forge Techniques

I realize this is a long aside to leave our bloom waiting, but as we’ll see, the remaining steps share a basic set of techniques, making it easier to discuss those techniques together.

Fundamentally, each stage of forging iron revolves around a basic cycle: by heating the metal, the smith makes it soft enough to work (that is, hammer into shape). Technically, it is possible to shape relatively thin masses of iron by hammering when cold (this is called cold-working) but in contrast to other metals (tin, copper and bronze all come to mind) nearly all serious iron-working was done ‘hot.’ In smithing terminology, each of these cycles is referred to as a ‘heat’ – the more heats a given project requires, the more fuel it is going to consume, the longer and more expensive it is going to be (but a skilled smith can often finish the work in fewer heats than an unskilled smith).

Via the British Museum, A Dutch drawing (c. 1624-1640) of blacksmiths at work, with the blacksmith himself in the center and a striker (with the two-handed hammer) to the left. An assistant mans the bellows on the forge to maintain the temperature.

A modern blacksmith can gauge the temperature of a metal using sophisticated modern thermometers, but pre-modern smiths had no recourse to such things (and most traditional smiths I’ve met don’t use them anyway). Instead, the temperature of the metal is gauged by looking at its color: as things get hotter, they glow from brown to dark red through to a light red into yellow and then finally white. For iron heated in a forge, a blacksmith can control the temperature of the forge’s fire by controlling the air-input through the bellows (pushing in more air means more combustion, which means more heat, but also more fuel consumed). As we’ve seen, charcoal (and we will need to use charcoal, not wood, to hit the necessary heat required), while not cripplingly expensive, was not trivial to produce either. A skilled smith is thus going to try to do the work in as few heats as possible and not excessively hot either (there are, in fact, other reasons to avoid excessive heats, this is just one).

One hot the metal can be shaped by hammering. The thickness of a bar of metal could be thickened by upsetting (heating the center of the bar and them hammering down on it like a nail to compress the center, causing it to thicken) or thinned by drawing (hammering out the metal to create a longer, thinner shape). If the required shape needed the metal to be bent it could be heated and bent either over the side of the anvil or against a tool; many anvils had (and still have) a notch in the back where such a tool could be fitted. A good example of this kind of thing would be hammering out a sheet of iron over a dome-shape to create the bowl of a helmet (a task known as ‘raising’ or ‘sinking’ depending on precisely how it is done). A mass of iron can also be divided by heating it at the intended cutting point and then using a hammer and chisel to cut through the hot, soft metal.

But for understanding the entire process, the most important of these operations is the fire weld. Much like bloomery furnaces, the forges available to pre-modern blacksmiths could not reach the temperatures necessary to melt or cast iron, but it was necessary to be able to join smaller bits of iron into larger ones which was done through a fire weld (sometimes called a forge weld). In this process, the iron is heated very hot, typically to a ‘yellow’ or ‘white’ heat (around 1100 °C). The temperature range for the operation is quite precise: too cold and the iron will not weld, too hot and it will ‘burn’ making the weld brittle. Once at the right temperature, the two pieces of iron are put next to each other and hammered into each other with heavy blows. If done properly, the two pieces of metal join completely, leaving a weld that is as strong as every other part of the bar.

From this demonstration, a series of hammer blows in the process of making a fire or forge weld. The sparks you see are flux and hammer scale (and possibly some amount of slag and excess iron material) being ejected out of the weld.

That’s not all there is to say about these processes (we’ll come back to them in a moment) but we now have enough of the basics to begin processing our bloom.

From Bloom to Billet to Bar

As you may recall, when we finished our process last time, we ended with a ‘bloom’ of iron: a spongy mass of pure, metallic iron interspersed with inclusions of waste materials called slag:

The iron of the bloom itself is also likely to be quite brittle because of these slag inclusions. This isn’t a product that can be sent directly to a blacksmith. It needs to be consolidated first into a billet and most of that slag needs to be forced out, both of which can be achieved via liberal application of fire welding.

This step is sometimes called bloomsmithing. The bloom is heated to roughly 1100 °C (gauged, as above, by the color of the iron) – it seems plausible that it may have been broken up into smaller chunks to make this more useful – and then hammered into a single mass through a series of fire welds. We’re not very well informed how this was done in the ancient world (save ‘with hammers’) because bloomsmithing doesn’t tend to leave a lot of evidence for us to observe. The end shape of the process was generally a very thick rectangular bar called a billet, ready for relatively easy transport.

This process has some advantages and disadvantages, beyond merely shaping the metal into a more usable and transportable form. Remember that our bloom contains a lot of material which isn’t iron (the slag); fire welding, especially when repeated, tends to expel this slag – as the iron is compressed in the weld, the slag is forced out. There is some debate (note Sim & Kaminski, op. cit.) if this process is sufficient to explain the very low slag counts seen in high quality weapons and armor, but it is certainly true that fire welding reduces the overall slag count. That means that we are going to see a reduction in the mass of the bloom at this stage, because we are ejecting waste material. That is going to show up in our efficiency as ‘material loss’ but only really because we didn’t have as much iron as we thought to begin with. That’s the good news.

The bad news is oxidation. We all know that iron rusts, picking up oxygen in the air to make iron oxides. At room temperature with normal humidity, this happens slowly. At 1100 °C, this happens very rapidly (because the high temperature encourages chemical reactions). Inside the bloomery furnace, this process was discouraged because the environment was oxygen starved, but blacksmiths cannot work in oxygen starved environments – they need to breath [citation needed] – which means our hot metal is going to begin to form a coating of oxides – rust – around it which is called mill-scale, or hammer-scale or just scale. The impact of hammering dislodges this material (often these are the sparks you see flying or the material you see shaken off of an iron bar during forging), but that means that the iron which had oxidized into rust is lost. Especially during a weld, with very high heat, that can actually result in meaningful material loss, particularly if many welds are required.

This process can be discouraged by the use of a flux, which mixes with the surface impurities (both forming oxides and also slag being forced to the surface) lowing their melting point below the temperature of the metal. This is crucial to prevent the impurities – because they form on the outer edge of the iron, where the weld is happening – from fouling the weld (‘burning’ it and rendering it brittle); it can also – as I understand it – allow us to get back some of the iron in those iron-oxides and prevent further loss of metal due to oxidation. There is some evidence that fluxes in iron-welding were in use by at least the Roman period and certainly by the Middle Ages were standard smithing practice.

Even with all of that effort with fluxes and using tongs or a frame to carefully consolidate our bloom, we’re going to end up with a lot less mass from slag ejection and oxidation that we started with. Sim & Ridge (op. cit.) estimate that the final mass of the billet consolidated from the bloom might be about half of the mass of the original bloom we worked to last time, but there would have been wide variance and no doubt skilled bloomsmiths would have done much better than inexperienced ones. It is worth noting that while any blacksmith likely could work a bloom into a billet, this job tended to be done by specialist bloomsmiths (likely working close to the smelting operation), rather than generalist blacksmiths.

Roman iron billets found at the legionary fort at Newstead, from Sim and Ridge (2002), pl. 8.

Billets tend to be fairly large and heavy and are likely to be cut and shaped into smaller bars for use and possibly for sale. Roman billets tend to be rectangular and fall into the 5-10kg range; Roman bars are rarer, suggesting that iron was probably sold and transported in this form and only forged into bars at the point of use. By contrast, in the Middle Ages, we see a bewildering range of sizes and shapes for metal ‘currency bars’ (Tylecote, op. cit., has a helpful table); Tylecote assumes the Greek obelos (roughly 1m long, 400g) was raw iron to be smithed, but given its use as a currency, I have my doubts. The bar shape has important advantages for the smith: the length of the long, thin bar creates a natural handle for the smith to hold, avoiding the necessity of having someone handling the iron with tongs for the entire forging operation.

Blacksmiths and Strikers

The image popular culture tends to present the blacksmith as a solitary craftsman, a depiction I suspect is heavily influenced by the fact that this is how most modern recreation and hobbyist traditional blacksmiths work. Apart from very well-funded and extensive places (for instance, like Colonial Williamsburg, which is one of the few places I’ve seen to recreate a multi-person forging operation) if you go to see a traditional blacksmith, you are likely to see exactly that: a solitary craftsman. And certainly, such small scale operations existed; we see them depicted in artwork but on the balance most forging seems to have been done in teams.

The basic tools of a smithy changed relatively little from the Roman period to the beginning of the early modern; we find the same basic set of tools in both. The core of a smithy was the forge, a charcoal-fueled fire with some form of forced-air induction (a bellows) which allows the smith, by manipulating the airflow, to control the temperature of the fire. Iron bars to be heated are thrust into the charcoal, both to better absorb the heat from the hottest part of the fire but also because that area, just likely the bloomery furnace, will be oxygen starved, discouraging oxidation (and possibly encouraging carbon uptake, in a process we will discuss next week!).

Via the British Museum, A Roman denarius (46 B.C.) showing the smith’s tools: tongs, an anvil and a hammer. Note that the anvil is a simple rectangular shape; contrast with the medieval anvil shown in the Armorer’s Guild Window from the Cathedral of Chartres below.

The hammering was done on an anvil. In the Roman period, most of the anvils we see are fairly simple rectangular or circular blocks of iron, although some have nail-holes to support heading a nail (see below). Over time, the anvil’s shape became a bit more complex, with one or two ‘horns’ added on the sides to make it easier to form round shapes with the anvil, along with a hardy hole used to seat hardy tools (also called anvil tools) on the anvil for making specialized shapes. It’s fairly clear ancient smiths had many of these same anvil tools, just not fitted directly to the anvil. I am not sure exactly when the more complex anvil shapes begin to appear; early versions of shaped anvils can be seen in medieval artwork of blacksmiths as early as the 1200s, but I could hardly offer this as a firm date (presumably an expert in medieval iron-working could pin this down with more specificity).

Beyond this, blacksmiths used a wide range of tools. Any good smithy would have a range of particular hammers with different weights and head-shapes for different purposes. There would also be tongs, although smiths preferred to hold the object directly whenever possible. There is a truly stunning variety of tools for making particular shapes and adjustments to the iron: punches (for punching holes), sets (a chisel for cutting the metal), fullers (for thinning the metal), flatters (a wide flat-headed hammer paired with a flat striking base for flattening out the metal), and so on. Blacksmiths were one of the few professions who could make their own tools and consequently any experienced smith would likely have a wide range of tools produced to fit his needs and preferences.

One thing you will not find much of in these smithies, or in the period artwork of them, is much in the way of protective equipment. At most, one often sees aprons (although these are absent as often as shown) in artwork showing blacksmiths; gloves are almost entirely absent. Every traditional blacksmith I have spoken to has simply said that getting burned by the sparks thrown off by dislodging hammer-scale or material thrown as part of the weld l is a part of the learning experience and, after doing it enough, one no longer much notices.

But what about the people? Blacksmiths in the pre-modern world were almost always trained through apprenticeship; there was no good way to learn the precise craft – so much of which relies on judging by feel or sight – other than by watching it done and doing it one’s self. In both the ancient and medieval world, it seems that it was common to pay a master smith to take on a child as an apprentice, but craftsmen also generally expected their sons to follow them in their crafts. Apprenticeships were long, with the apprentices working as unskilled or semi-skilled labor in the smithy while also learning their craft.

But a blacksmith who had gone through this training process was a valuable skilled worker and so it should come as no surprise that an effort was made to essentially multiply his labor to get the most out of that skill investment. A master smith might work alone but was more often the center of a team of semi-skilled and unskilled laborers, the most common of these being strikers, who served to effectively multiply the blacksmith’s labor. A blacksmith working with strikers would generally hold the iron with the left hand and, using a lighter, one-handed hammer in his right hand, tap the metal where he wanted the next blow to fall (the strength of this blow – or sometimes a series of blows delivered against the anvil first – signaled the force that the blacksmith wanted); that blow was then delivered to the desired place and power by one of the strikers, who used a heavy two-handed hammer. The heavy blow with that hammer would both move more metal, but also, by using multiple strikers, the team could work more quickly without exhausting themselves.

Via Wikipedia, Roman bas-relief in marble of Hephaestus forging the arms of Achilles (here making or attaching the thin bronze cover which would go over the wooden core of the shield) and working with three strikers, who are presented as Cyclopes. Athena and Achilles’ mother Thetis watch.
One quirk of this particular image is that this is clearly bronze-work being done; it is thus likely that the shield is being cold-worked, rather than hot-worked as we’ve discussed with iron. We’ll get to how bronze is worked in a later post, but it is often hammered cold rather than hot.

The maximum number of strikers that might work with a single blacksmith is generally three, but that isn’t the limit of a single blacksmith’s team. He might also have another person tending the forge-fire, working the bellows and watching the heat (a good job for a junior apprentice) and possibly even a second smith (perhaps a senior apprentice) doing semi-skilled smithing work, like barsmithing or nail-making, on a second anvil. For an armor-smith, producing the large quantity of wire required for mail could also be done effectively by unskilled labor (we’ll talk about how that was done next week).

In terms of social status, our sources are clear that blacksmiths, while skilled artisans, still belonged to the ‘lower’ classes, although perhaps quite close to the top of them. Blacksmithing was one of the artes mechanicae (mechanical arts fit for low-status workers) rather than the artes liberales for high status men (though literally “the arts of free-born people”). While the Greeks and Romans had their blacksmith gods (Hephaestus and Vulcan respectively) it is striking that they are often very explicitly treated as lower-status ‘blue-collar’ gods compared to the rest: Hephaestus is ugly, lame and his marriage to Aphrodite is presented as something of a humiliation for her in some versions of the myth (cf. Hermes, the other decidedly ‘blue collar’ Greek god). In Florence, which ranked its guilds by status and importance, the Arte dei Fabbri, the guild of blacksmiths, was typically ninth or tenth, behind guilds of bankers, cloth and silk merchants, lawyers, physicians and such.

Via Wikipedia, the coats of arms of the major guilds of Florence, 18th century. The Fabbri – the blacksmiths – are the second from the left in the third row, marked by their tongs. You can actually still see buildings in Florence marked by the standards of their guilds, including the tongs of the Fabbri.

That said, within the laboring classes, a skilled blacksmith rated quite highly. Master smiths seem to have had a significant earning premium, even when working on basic goods; Lee Bray (op. cit.) notes that going by prices contained in the Vindolanda tablets for both raw iron and finished nails, a blacksmith making even such relatively simple objects as a set of nails might see 20-30% increase in value over the cost of the iron, even after material loss in production is accounted for. The potential increase for high-status items like armor or weapons could be even higher. Specialist armor- and weapon-smiths, who provided their goods directly to the nobility seem in particular to have been held in relatively high esteem. Moreover, from the Roman period on, we see blacksmiths in larger towns tending to band together to form guilds, both to monopolize the trade but also to wield considerable political influence. We see guilds of these smiths doing things like endowing stained-glass windows on Cathedrals, which speaks to their wealth and influence (as with the window from the Cathedral of Chartres, below):

Via the University of Pittsburgh, armorers working, both on an anvil and also polishing, from the Cathédrale de Chartres (c. 1210).

Other laborers in the smithy might not have been quite so fortunate. Apprentices, of course, were proper blacksmiths in training and might one day look to be as well respected as the master from whom they learned their trade. But for the up-and-coming apprentice, the blacksmith’s guild was an obstacle, not a helper; it was in the interest of the guild members to restrict new entry as much as possible in order to avoid competing down their prices, which may have left those who finished their apprenticeships (‘journeymen’ in the parlance), stuck in subordinate positions until age and death opened up space in the local guild for a new master.

Things were worse for the many strikers and other laborers who were essentially unskilled hired hands or even enslaved laborers (given their depiction in artwork, it seems likely many ancient strikers were slaves) of much lower status and who could not expect to be trained into blacksmiths themselves some day. While some strikers were probably apprentices in training, it is quite clear that not all of them were! These workers would also have been far less richly paid; indeed, the entire point of strikers was to have laborers who could be paid very little but still amplify the production ability of the blacksmith himself. We should also keep in mind that the women of the household would often likely have been involved in tasks around the smithy in support of its main operation, although the nature of our sources has rendered much of this work invisible to us.

Forging Some Examples

Now, as I said up at the top, each iron object tends to have its own set of processes needed to produce it. While blacksmiths absolutely could experiment, its quite clear from the artifact record that most blacksmiths were largely following the patterns of steps, with only small refinements, that they had learned themselves during their own apprenticeships. This is one reason, as an aside, that pre-modern weapons technology (things like the shape of swords or armor) can be seemingly so slow to adapt to changing conditions: craft knowledge works best as steady refinements to accepted practices, rather than radical changes (although the latter is certainly possible, especially if what is happening is that a new object-type is being adapted from another culture complete with its own well-established process). Still, for the sake of illuminating how this might work, I’m going to give just a couple of fairly simple examples.

Please keep in mind through this that I am not a traditional blacksmith, so I may get these steps slightly wrong. Note that for each one, I’ve linked a video of the method; the description may not make much sense without also watching the video.

Let’s start with something very simple: making a nail (note that we are going to mostly focus on the nail shape here; Roman nails were actually often carburized into mild or medium carbon steel, which we’ll deal with next week). I’m not going to say ‘we reheat the iron’ after each step, but you may safely insert that every time; this is all hot-working (my impression is that a nail is generally done in three heats). We start out with a bar that we are going to draw until we have something close to our desired thickness just beneath the head of the nail. We’re then going to continue drawing out the shank of the nail to create our taper. If you ever wondered why ancient nails tend to be square in section rather than round, this should explain that – we’re using a flat-headed hammer to hammer the shape and complete its taper, which produces that square section. I have seen some guides that suggest using a fulling tool to begin tapering out the nail (Sim suggests this) but it doesn’t seem necessary from when I’ve seen it done.

Once we have the shank of the nail about into shape, we use a set and a hammer to cut the nail off from the parent bar, just above the taper. Finally, we use a heading tool – in the ancient or medieval period, this would often have been a board with a hole that the nail, but not the thickest section of the bar left attached, can slide through. A modern smith might just use a vice. We slide the nail through and then hammer the head flat, upsetting it, in blacksmithing terminology (by which we mean, thickening it) to create the flat head of the nail. And there have a nail. If you want to see these steps illustrated in practice, this video goes through all of them and explains them fairly well.

For something more complex, we can look at two ways to make axe heads. One method – demonstrated here – is to begin with a fairly thick block of iron. Once heated in a forge, a punch is used, rather like hammering in a nail, to drive through the body of the iron to create the hole for the haft. Then what will be the blade of the axe is notched using a fuller to create the particular axe pattern and then the iron in front of that notch is drawn out to create the blade of the axe. As the edge is drawn out, note that the blacksmith is using the side and edge of the anvil to carefully control the shape and thickness. Finally, and this is a crucially important step for any blade, the cutting edge is filed down (in the video using a machine, though this would have been done by hand with files in a pre-modern workshop – quite a lot of the work of making metal objects was in the filing).

Part of the reason the smith above can use that method though is that he is using uniform metal (probably steel) throughout. We’ll talk about steeling next week, but using an entire block of steel was not always an option, so we see folding over operations with axes as well. The method is demonstrated here. Rather than beginning by punching a hole in the bar, we begin by hammering the bar into a long, flat rectangle (that is, drawing it). That is then heated at the center and bent over, creating the eye for the half in the curve of the new bend. Then a higher quality piece of iron (the ‘bit’), typically steel as compared to the pure iron of the rest of the axe, was inserted between the two sides of the iron axe head and then all three elements were heated and fire-welded together, leading to an axe-head with an iron body but a mild-steel edge that could hold it sharpness and cut much better.

(As an aside, both Tylecote and Sim & Ridge have good pencil drawings of the forging stages of a lot of common weapons or tools. Bealer has even more detail and includes much more discussion of the practical concerns of actually executing on these methods.)

Limitations

I want to close out this post by noting some limitations in this sort of production. A skilled blacksmith can work iron into almost any shape, but there are some crucial limitations in size and shape which are important to understand.

The first is size: because all of this work is done by hand, and because the forge and anvil are only so large, there are real limitations to how large a piece of iron can be produced by these methods. Of course a larger iron may always be welded together, but it has to fit into the fire first! In practice, making single pieces of iron much larger than a large sword or breastplate was generally impractical and sometimes impossible. This is one thing that fantasy settings often get wrong, assuming that things like large metal girders or heavy metal armor plates (for armoring things like towers or rams, for instance) could be produced in iron by a blacksmith. Very long staves could be produced, by welding multiple staves together, but that process imposed practical limitations on the thickness of those staves.

The second issue is a set of shape limitations. Truly hollow structures were very difficult to create, especially if they had to be able to withstand significant amounts of force. There is, after all, no way to get inside a small hollow structure to hammer it outward (and a larger hollow structure will be impractical for the reasons above), while fire-welding thick sections of metal over a hollow (as for instance, if you tried to make a tube by folding a long sheet of iron over into a tube shape) is going to force iron into the hollow (also the many, many welds required along the length of that tube are going to require a lot of heats and could create very uneven strength).

Via Wikipedia, the Athlit Ram, a 465kg naval ram cast in bronze, probably from a quadrireme. This is the sort of large single piece of metal that would be practically impossible to make in wrought iron. Because of the forces it underwent during a ramming attempt, the ram had to be a single piece, to hold up.

Finally, producing objects of truly uniform thickness is effectively impossible using only these methods. That’s not necessarily the huge weakness it initially sounds like; armor plates were rarely uniform in thickness and a good armorsmith could carefully manage thickness to maximize protection where it was needed most and save weight (and, as a quick aside, as Sim & Kaminski discusses, there is some evidence to suggest that the Romans may have been rather more sophisticated in the production of sheet metal). But the fact that every object forged was just a little different because of the hand-hammering method matters a great deal when it comes to things that need to fit together very precisely.

All three of these limitations actually come together quite clearly in the effort in Europe to produce strong iron cannon barrels. Wrought iron was far superior to cast iron or even cast bronze, but the ideal cannon shape – a very large (bad) tube (bad) of uniform thickness exactly matching the thickness of the shot (bad) – was functionally beyond the power of even the most skilled smith to produce. Instead, many early iron cannon were build up using hoop-and-stave construction, with individual iron bars being arranged around a wooden core, compressed in by iron hoops (heated to fit over the staves so that when they cooled, they pressed them firmly together), with one side blocked by a breech block held in place by the pressure. The wood was then burned out to create an open barrel. Such a construction allowed for a wrought iron cannon, but the barrel diameter was hardly consistent and the hoops could burst while firing.

Via Wikipedia, a 200kg wrought iron bombard, made using hoop and stave construction, with the iron hoops holding the piece together clearly visible.

In practice, these limitations meant that even well into the iron-age, things that required precision, uniform thickness, careful replication or difficult hollow shapes were often still made in bronze, which could be cast more easily (though naturally some of this varies by the skill of the blacksmiths; the Gauls were making iron helmets by the 300s B.C. whereas the Romans still used bronze at that time).

And that about covers shapes. But as I mentioned, iron-working isn’t just about the shape of the object. Instead the very way the thing is made changes its fundamental characteristics, like hardness and ductility. And so next week we’ll close out this look at iron production by looking at how a blacksmith might manage those facets: work-hardening, tempering and, of course, steel.

54 thoughts on “Collections: Iron, How Did They Make It, Part III: Hammer-time

  1. breaks immediately without behind, -> breaks immediately without bending,

    hard hard brittle materials -> have hard brittle materials

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  2. Blacksmithing has some really interesting folkloric connections. The special skills required to work metal can seem like a kind of magic, and of course smith gods are rather popular. I read somewhere that the use of arsenic in bronze smelting may have caused deformities, inspiring the image of the lame smith ala Hephaestus.

    As another example: Africa. Iron working was developed in West Africa without an intermediary Bronze Age, and metalworking was traditionally seen as a kind of practical magic (not so different from many other cultures, mind you). Because of this, blacksmiths were sometimes seen as witches and were ostracized despite their useful skills. It varies from culture to culture, of course, but generally in cultures where blacksmithing was the work of a hereditary caste, or among pastoralists, they’re more shunned, while other cultures valued them as highly as European ones did.

    One particularly noteworthy example is the Beta Israel, or Ethiopian Jews, who were hereditary blacksmiths and who were popularly believed to be werehyenas in addition to semi-magical metalworkers.

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    1. out of curiosuity, how did sub-saharan africa develop iron working without progressing through a bronze age first? was it knowledge brought to them through trade with the Mediterranean, or was it just a quirk of their cultural development? (i know that copper and tin are not terribly common, so i could easily believe that they didn’t have a major bronze working period, as the bronze age in the Mediterranean and asia were largely due to quirks of geography regarding easily mined mineral deposits and ease of trade via sea travel and rivers)

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      1. I have seen an article which claims that middle-Niger iron-working remains pre-date contact with the Mediterranean. It was previously assumed that iron-working filtered down through the Sudan. I’ll try to locate it.

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    2. My understanding is that the source of the “lame smith” stereotype is rather the reverse of what Matilda suggests. Lame boys could not work effectively in the fields, or in many other trades, and therefore were likely to be apprenticed to (or otherwise set to work as) blacksmiths.

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    3. If the Beta Israel were in fact descended more than theologically from the Twelve Tribes of ancient Israel, it’s entirely possible that they brought their metallurgy traditions into exile with them. The Israelites were using both bronze and iron weapons in King Saul’s time (1100 BC or so), according to the Old Testament.

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      1. In general good technique in joinery tends to prefer cut joints, as I understand it. My brother-in-law went through a long apprenticeship as a master joiner, and he mentioned that anyone using unnecessary nails was referred to contemptuously as a ‘carpenter’. A well prepared wooden joint, especially in something as big as a building, should be stronger and longer lasting than an iron nail.

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  3. it is worth noting that once the knowledge for things like gears was developed, the need for strikers could be reduced some through the use of hammer mills. where rotary power (provided by waterwheels or animals) which through gearing could be turned into up and down motion through the use of camshafts and triphammers. which provided a (fairly) regular motion that could be used to hammer the metal. we know that such tech was in use during the later middle ages. the basic knowledge of the tech required dates back to the greco-roman period though, we just don’t have enough evidence that it was in use for that purpose. note that the same tech can easily be used to run bellows to help keep the furnace hot, and other such uses. often off the same motive source.
    (the trip hammer can also be used for the processing of the Ore, being used to crush it prior to smelting for example.
    the reason we call them ‘mills’ is because the gearing technology was more widely seen to turn grindstones for producing flour, and the terminology got applied to other uses of the concept, luch as lumber mills and hammer mills in forges and mining.

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    1. Reminds me of my late granddad’s reason for scorning the meso-American cultures of the Aztecs and Incas: they had wheels and knew what they were good for (their kids had wheeled toys before the Spaniards showed up!) but there’s no evidence that they made much practical use of them for technology; by Granddad’s account, work’s what they had slaves for.

      The reliance on slave-labor (as above, with the strikers) rather than engineering labor-saving machines may well be why hammer-mills were such a late invention.

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      1. 1) Incas are South American, not Mesoamerican.

        2) Wheels do best on smooth flat ground. Mexico is kind of a mix of mountains and jungles, and their capital city was a bunch of linked islands in a lake; the Inca region was *very* mountainous, with roads that contained a lot of outright stair segments.

        I imagine they could still have used potter’s wheels or wheelbarrows, but the lack of wagons is bigger than “duh, just didn’t think of it”.

        Plus even in Eurasia the wheelbarrow seems to have been a very late invention. *Maybe* classical, but then European evidence starts around 1200 AD! Even in China it seems to be an AD thing.

        A Quora answer notes transport wheels benefit from iron rims, and metal hubs and axles, which weren’t available. It also notes of the North American travois:

        “Only one set of ends of the branches touch the ground, minimizing friction and surface impacts, while a surprising amount of weight can be moved all day by dogs or people in a simple harness. It’s a more practical solution than building wooden carts for roadless terrain without blacksmiths, wheelsmiths, wagonmakers, sawmills, harnessmakers, etc..”

        And

        “Intriguingly the symbol of the “Medicine Wheel” (anything we don’t immediately see in practical use is abstract religious symbology) that appear from Northwestern Canada down to the Valley of Mexico apparently as part of the Ute-Aztec migration is a spoked wheel. While used for calendar functions based on the spokes lining up with celestial events, solstices particularly, it’s an odd way to do it if you’d never seen a wooden spoked wheel before.”

        https://www.quora.com/Why-did-the-Maya-Aztecs-and-Inca-not-invent-the-wheel?share=1

        Another answer says

        “The wheel was invented in one of two places: Mesopotamia and the plains of Central Asia somewhat to the north of Mesopotamia. If you were to visit those places, one of the first things you’d notice about them is how flat they are. They’re composed of large expanses of hard, even ground, which is one of the hidden prerequisites to developing the wheel. “

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  4. This.is.not.sparta!
    how were they getting their weapons and armor ? from hilots blacksmiths since Spartans were forbidden to do any work ? but it’s a bit awkward to get your weapons from your enemy, since hilots were officially an enemy Spartans were declaring war to every year. Also if blacksmiths were hilots, well, punishing insolent slaves by cutting off some part like a hand was just losing an experimented worker. How were Spartans getting good fighting gear then?

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    1. From the perioikoi, the working class, obviously. Non-working spartiates were only a minor percentage of the spartans in total.

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    2. Weapons are less important than food, but they got their food from their helots. A reign of terror is good way to ensure that people do more or less what they need to do.

      Liked by 1 person

  5. This is reminding me of The Blue World by Jack Vance. In this sci-fi story humanity lives on what resemble giant oceanic lily pads so mining is impossible. Eventually they obtain iron by boiling down blood. They only get a little so they use it for spear heads and the like.

    Would this be possible at all? Even with very large amounts of blood and very few spear heads?

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    1. Using metals accumulated by living organisms is definitely a thing. The slimy brown mud produced by iron oxidising bacteria can be smelted (see: primitivetechnology’s youtube channel). On an industrial scale plants (phytomining) or microbes (bioleaching) can be used to concentrate metals from ore too low-grade to be economical to process the normal way.

      Blood, OTOH, is probably not a good way to accumulate iron. Maybe large-scale use of fish blood would work but it’s probably easier to extract iron from whatever the animals ate to get that iron.

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      1. In the story they don’t use fish blood (it’s an alien world and native species don’t have iron-based hemoglobin) but rather donated human blood.

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    2. It would be possible to do it, but as guessed, it would be a horrendously inefficient source of iron.

      Looking up some numbers: blood has somewhere around 150 grams of hemoglobin per liter, possibly other iron containing protein that I don’t know about. That hemoglobin itself is about .4%(not a typo) iron by mass, so you get about .6 grams/liter of blood. To get this iron, you could in theory boil down and burn blood (to get rid of the water and organicc stuff) if done properly you get a bunch of metals/metal oxides/random other heavier elements, which could than be separated as appropriate (partial melting and other processing) The process would have to be very, very good, since the amount of iron is so small, and it would be very easily contaminated by other stuff.

      Getting iron from food a would be a similar process, its hard to say which would be more efficient (iron from food is probably even less concentrated than iron from blood, but would supply more total iron).

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      1. Emmet Asher-Perrin, a columnist at tor.com, wrote an article “How to Actually Make a Sword ‘Forged From the Blood of Your Enemies'” (https://www.tor.com/2017/07/20/sword-forged-from-the-blood-of-your-enemies/). It is an amusing and somewhat disturbing read.

        The amount of iron in a human body is about 60 ppm by mass (https://www.webelements.com/iron/biology.html), so an 80 kg human will have about 5 grams of iron, total, in their body.

        Of course, other metals are even worse. If you want to make bronze (copper plus tin), copper is about 1 ppm and tin is about 0.2 ppm. Zinc is about 33 ppm.

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  6. Normally I don’t leave comments, but I just have to say, I love this series of articles, on the subject. Thanks for posting them, I am looking forward to seeing more of them 🙂

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  7. Do you know why they didn’t bore out the central section of a cannon? I would have thought if you rough out the shape with the hoop and stave construction you mentioned, the obvious next step would be to use a lathe to ensure a uniform profile.

    I haven’t tried it myself, but I don’t see why this should be impossible with a hand-lathe, provided that the operator was very skilled.

    Also, do you know when something like a shaper would be a plausible tool for a blacksmith to have access to?

    I would have thought that between a shaper and a lathe, it’s possible (if difficult) to make more or less arbitrary parts – and neither shaper nor lathe are particularly complex in and of themselves.

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    1. According to William McNeill’s “The Pursuit of Power” (1982), pp. 167-70, the boring of cannon was invented by Jean Maritz and his son, also named Jean Maritz, in the first half of the 18th century, and it required a good amount of technological innovation to bring to fruition.

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    2. Mostly because while wood lathes have existed for thousands of years, precision lathing wasn’t a thing until the 1700s. You need better metalworking to make a lathe capable of boring out that much steel. And in fact one of the first important uses of precision lathing was making much stronger and more accurate cannons.

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      1. George Dorn has it correct. To bore out cannon barrels with the level of precision you need, you need better drilling devices and better metallurgy. To get a single hunk of metal to drill, you need to be able to cast it, which requires better metallurgy. The quest for better cannon actually plays a huge role in the early industrial revolution, particularly because the technology for boring cannon was basically the same as the technology for creating cylinders for use in large steam engines.

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        1. The cannon was cast hollow, and the bore machined to uniform diameter. Even now, machining a large-diameter bore is tricky (done to re-line hydraulic cylinders, for instance), and a job best done by an experienced machinist

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          1. In the 18th or early 19th century, they stopped casting iron guns with a bore; instead, they would cast them solid and bore them out.

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  8. My grandad was a blacksmith’s boy at a relatively traditional blacksmith’s in the UK in the 1930s, and still worked in a team like you describe, graduating to striker before going off to war and other things. I remember watching a film with him where a Roman officer was wearing a steel-looking ‘muscle cuirass’ and he said authoritatively ‘that would never be steel, they couldn’t make that’’. I looked it up afterwards and ‘muscle cuirasses’ were indeed always made from leather or bronze, sometimes plated with silver or gold. But why couldn’t it have been steel? And why didn’t the helmets have the same limitations?

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    1. The Cyclopes are often depicted in classical works with a normal face that, for lack of a better description, has room for two eyes and even has eyebrows. However, their eyeholes are empty, and then they have an eye on the forehead. See for example this picture from wikipedia: https://en.wikipedia.org/wiki/Cyclopes#/media/File:Head_of_a_Cyclops_Colosseum.jpg
      I am not sure if that is what is going on here–it’s hard to get a good look at the foreheads, and I could not find a better version of this photo to look at carefully.

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      1. Someone once pointed out to me that there was a species of dwarf elephants on Cyprus, and that elephant skulls look like they ought to be Cyclopean.

        First relevant hit found was https://ccccomedy.wordpress.com/2015/01/27/the-dwarf-elephant-of-malta-origin-of-the-cyclops-myth/

        :A possible origin for the Cyclops legend, advanced by the paleontologist Othenio Abel in 1914, is the prehistoric dwarf elephant skulls – about twice the size of a human skull – that may have been found by the Greeks on Cyprus, Crete, Malta and Sicily. Abel suggested that the large, central nasal cavity (for the trunk) in the skull might have been interpreted as a large single eye-socket. Given the inexperience of the locals with living elephants, they were unlikely to recognize the skull for what it actually was.:

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  9. Bret, here is a longer list of typos, including corrections for problems noted already by mindstalko, above:

    avoid this coming confusing –> ….becoming confusing
    these treats are not binaries –> these traits
    One hot the metal can be shaped –> When hot…
    they need to breath –> they need to breathe
    lowing their melting point –> lowering
    period and certainly –> period, (comma inserted)
    tends to present the blacksmith as –> …present is the blacksmith
    artwork but on the balance –> artwork,… (insert comma)
    just likely the bloomery –> just like the bloomery
    the weld l is a –> weld is (delete stray I)
    And there have a nail –> there we have…
    eye for the half–> eye for the haft
    hold it sharpness –> …its sharpness
    cannon were build up –> …were built up

    btw, this one: “blacksmith gods…it is striking that they” generated the appropriate groan for the pun

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  10. Ah, now we get to the hammering.practically all I know about ancient and medieval ironworks is the high cost in trees and that it’s hammered into shape not cast.

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  11. I think it might be worth noting that upsetting tends to be harder than drawing, so you’d rather start with a shorter, thicker billet. Also, pre-modern smiths used more forge/fire welds than modern smiths do, often because they were working with smaller pieces of iron.

    Also while grinding/filing/polishing was a huge part of the process, pre-modern smiths would have tried to minimize it by forging close to the final shape whereas modern knife makers might take a heavy, vaguely knife shaped bar of metal, and turn it into a sleek kitchen knife on the grinding wheel.

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  12. In your series on farming you made a point that efficiency was not the central concern there like it is with modern farmers. Instead they sought to minimize risk. Is there a similar factor at play here? I’m thinking in particular about all this iron being repeatedly cooled. Heat it for roasting, then let it cool. Heat it for blooming, then let it cool. Heat it for bloomsmithing, then let it cool. Heat it for forging, then let it cool. Every time you let it cool you lose the heat energy of all those trees you charcoaled to supply the heat in the first place. Was effort ever made to prevent loss of heat between these stages such as by moving quickly from one step to the next or by insulating the material?

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    1. I think there is maybe some risk minimization, in that a blacksmith, while well-off, does need to work in order to live. However, iron seems to be in constant demand, and the supply not particularly fragile, so as long as the total number of blacksmiths isn’t too high the blacksmith’s labor will be comfortably valuable. Guilds take care of that problem.

      An injured blacksmith might be in a bit of trouble, but the guild might help out in those times, or even the blacksmith’s network of friends, if those are indeed distinct.

      However, inefficient use of fuel doesn’t appear to increase reliability, unlike in farming where the efficiency-reliability tradeoff starts with the planting of a balanced mixture of crops instead of whichever produces the highest yield.

      SPECULATION FOLLOWS: I am guessing about this based on my second-hand passing knowledge of blacksmithing. The roasting consumes fuel in order to distribute heat throughout the fuel to be roasted. Given the heat transfer process, which seems like it might be quite inefficient, the fuel is consumed to reach the appropriate temperature. If you cool it off afterward, that’s a small loss. If you had a bloom furnace right there you might be able to pick directly from the roasting furnace and place into the bloom furnace. Maybe that was even done?

      As for the forging, both the bloom forging and the functional forging afterward, I think the variable that determines fuel consumption is the total number of heats. If the bloom can typically be forged completely in one heat, then yes you might gain from trying to eke out a simple forging from the same heat. Maybe for nails? As the number of heats increases, for the bloom and the product, the wastage in shipping (possibly just across the street?) a billet to another smith for forging into a final product decreases.

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  13. “Instead, many early iron cannon were build up using hoop-and-stave construction”

    Basically, they were barrels, but made entirely of iron, rather than wooden staves and iron hoops. Hence presumably why we still talk about “gun barrels” rather than “gun tubes” or “gun pipes”.

    Liked by 1 person

  14. I watched a couple of videos by a modern, yet comercial, blacksmith on youtube the last couple of weeks. That makes me think an important part of why we think of black smiths as working alone, is the fact that blacksmiths work with powertools for at least the last 150 years or so.
    A power hammers takes away the need for a striker, and powered bellows replace the need for a guy watching the fire. At most you need a seconed person holding the tongs, for a bigger piece.

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  15. I am loving this series like all the others. This is sort of in my wheelhouse so thought I would risk a few comments.

    To see the great example of the process I would recommend the video “Ore to Axe” by Ken Koons. They show everything from collecting the ore, roasting it, building the bloomery, smelting it, working the bloom to a billet, and forging an axe. Highly recommended whether your are curious or interested in doing it yourself.

    On the conservation of heat, I think they were conscious of it but often other issue trumped it. Most smelts I have seen when they first pull the bloom out they use the residual heat in it to try to forge it down a little but the heat doesn’t last that long and the bloom doesn’t always cooperate. You’ll have to reheat it fairly soon. Trying to pick out the ore from the ashes of the roasting fire fast enough and then get the hot ore to the bloomery presents a handling issue. It also presents a timing issue, the bloomery is being fed constantly, roasting a lot of little batches of ore and have them ready at 20 minute intervals is difficult. You do see the conservation of heat in the forging though. Historic smiths would typically start forging something at one end and, heat by heat, work toward the other versus jumping around.

    I think the limitations, as stated, might come off as a little more absolute than reality. Or at least biases towards the production of cannons,

    For size, correct, if you are talking full sized cannons that is out of reach. A mass the size of, say, a decent anvil could be forged with human power, especially if you are talking about forge welding on the feet, heel, horn, etc. A team of good strikers with long handled sledges (the radiant heat of that much iron at forge welding temp is something to experience). I have an old black and white chain factory video were quite large pieces of steel, bigger than most my anvils, is being worked by a dozen strikers with hammers.

    Uniform thickness depends on how uniform you want/need. For the most part it wasn’t needed so you wouldn’t spend the time, effort and heats on making it so. You can make a lot of complex machinery, locks, etc. using traditional methods without uniform dimensions. Multi-piece devices were made a piece at a time to fit the rest the device.

    Barrels for rifles and pistols can be shaped and forge welded together with a swage and mandrel. It is a long process and you have to be a good smith to know the weld it solid enough for use as a functional firearm. Certainly not for cannon size. If it isn’t going to need resist the strength of gunpowder forge brazing the seem, (essentially gluing the seem shut with brass using the heat of the forge) on a pipe works fine.

    For nails, if a smith has made enough for a house, say 30,000 they get good and should be able to knock out a nail with one heat. You would have multiple irons in the fire, by the time you finish working the last the first should be up to temp. If you are too slow or have “too many irons in the fire” they’ll start to burn up before you get back to them. If you ever have the chance watch Peter Ross, former Williamsburg smith, forge nails. He is a machine in both speed and repeatable precision.

    Guilds and “advances” in design. I have heard that one of the things Guilds did was decide how things were going to be made. An ax was going to have this shape, include this much steel for a bit. If you came up with a great improvement you couldn’t just go into production of it of it without running afoul of them. That is -one- of the reasons you saw things like axes start to evolve quickly in the New, Guild-free, world. I couldn’t back this up with any citations though.

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    1. Note that most houses would not have had many nails. Using thousands of nails in a house didn’t happen until mass production made it possible to turn out nails in mass quantities for cheap. Nails would have been reserved for places where you couldn’t use a peg or other joint for some reason.

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      1. Correct. Framing, etc. was done with various joints, like mortise and tenons and dovetails, and secured with wooden pegs and still were when nails were available. Since iron and wood expand and contract at different rates in heat and humidity nails weren’t always the right fastener for the job. This expansion and contraction is the reason nails in door were clinched or “deadened” by driving them through the door, bending them over into a hook pointing back at the door, and driving the hook back into the wood. This is where the saying “dead as a doornail” came from incidentally.

        There are some applications where nails excelled. Attaching wooden shakes on the roof? Nails are much better than most alternatives. Clapboard siding and wood flooring? Lathing for plaster? There are obviously other ways of accomplishing these, or building in such a way that you avoid the problem altogether (log-on-log building, thatched roof, etc.) if you are in an area with different resources but in “industrialized” areas nails could be had and you would probably be looked at oddly if you used some nail-free techniques. The 30,000 nail estimate comes from memory from a conversation with a Williamsburg smith recounting how many they need to make when they build a new building. The conversation was a while ago and I have been known to eat paint chips so actual mileage might vary.

        As far as mass producing nails for cheap, I think that happened much earlier than most people think. Not machines making cut nails but nailers, specialists who -only- forged nails, all day every day, hammering them out. Specialization and mass production happened relatively early. I’ve heard estimates that a good nailer could turn out a nail every 20-30 seconds all day. The excavation at the Roman fort at Inchtuthil, built in 82 or 83 AD, included a hoard of about 7 tons of nails so it isn’t like they were rare. Then again, these were Romans and after the whole Spartacus thing so maybe they were just tired of dovetailing people to crosses.

        Besides specialist nailers others (later than Romans) were produced through a true cottage industry method, think a farm family in winter sitting around a fire with nail rod, hammers, headers, and anvils not much bigger than the hammer. If you can’t farm it isn’t a bad way to make a little extra money and a good excuse to sit around the fire when it is cold.

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