Monday, August 31, 2009

Bronze Working

This is a fairly straight-forward subject, discovered probably by accident by a potter who noted that certain rocks melted when placed in the airless ovens which were in use around 6000 to 4500 BCE. Still, it was another thousand years before certain localized areas had learned how to forge bronze into hard materials, through introducing an impurity into the metal (arsenic was used long before tin).

Certainly localized cultures with copper and arsenic available, and later tin, benefited from the slightly lower melting point for metals forged at or near sea level: the Indus, Nile, Tigris-Euphrates and Yellow river valleys. Bronze was considerably stronger than copper, and once the process of forging was discovered, an item could be hammered until it was up to four times as strong as the metal when cast.

This led to bronze weapons and armor, which were the power weapons of their day ... enabling those river valley civilizations with the process to war successfully against their neighbours, thus unifying each culture for long periods. Although all were subject to infighting, the cultures became homogeneous in language, religion, political structure and social custom.

Thus, individual cultures were melded into Egyptians, Mesopotamians, Aryans and Chinese. As metalsmithing spread out into the hills, those tribes too unified – as the strongest dominated the weakest through the use of metal weapons.

It is a point that very few cultures have been successful at all without the discovery of metal, and none at all who were at some point in their history exposed to metal-wielders. Wood does not stand up well to metal – not even when the wood includes the bow and arrow, as most cultures did long prior to the discovery of metal weapons.

That is because early bows and strings are notoriously unreliable, and lack the power of the later longbow for overcoming heavy armor. Early bronze armor, incidentally, was little more than a large plate which hung on a strap around one’s neck, covering the front of the body – often of burdensome weight. But it was tremendously effective in battle, compared to those relying on non-metal armours. Thatch and leather had been effective against wooden weapons – but were not so much against a hard bronze sword with the benefit of an edge.

It is often thought that bronze is inferior to iron where it comes to weapons. I haven’t been able to find any data to support that conclusion. Copper was more easily identified than iron by the neoliths, and occurs more often in placer deposits (pure metal nuggets). Copper melts at 1,083 degrees Celsius, while iron melts at 1,535 degrees C. Thus it is easier to manufacture. When beaten and annealed, bronze is as hard and as dense as wrought iron – meaning that for two dark age knights hacking at each other with swords, a bronze sword is just as effective (and no more likely to dent or bend) than an iron sword.

However, it was discovered that iron – once identified and once means to found it was managed (quite early on, not long after the discovery of smelted copper) – is vastly more plentiful. Its appeal rose because it was as good as bronze and much cheaper. It was also available in a greater number of places.

By the time of the Middle Ages, copper in many ancient mines had played out, not to be found in many new places – and tin, the best addition to copper, was much rarer. Bronze fell out of favour.

From a D&D perspective, any truly ancient weapon ought to be constructed from bronze ... at least it would be a good indication that the weapon came from another age, and was made according to principles that were lost. That is the usual program, is it not? Was Excalibur necessarily made of iron?

But then we see weapons presented in movies as shiny, lightweight artifacts – not as metal clubs with points and edges. Without question that is how early weapons were used. Daggers and swords were heavy, the heavier the better, since that helped hold the edge and produced the best hit possible.

I feel both mirth and disgust at watching the fight scenes from the movie 300, which features weapons of iron with remarkable sharpness, slicing bodies apart as though they were not made of hard bone. Mystically, we are taught by the movies that weapons don’t dull and that if you swing hard enough, the human body offers no greater resistance than warm jello.

Granted, those scenes are for iron weapons and not bronze, but the principal is the same. As I say, a bronze weapon will match the power of an iron weapon, weight for weight. It was not until the 17th century that harder iron metals were managed.

This is not very helpful for your campaign, I know. You may consider that for the time period, the power of the priests, the development of cultures, food production and so on were brought together by the creation of bronze weapons to form what we think of as the Bronze Age. I will write more on this tomorrow, as I hope to introduce a unifying principle into these technologies.


R said...

These posts are actually quite helpful for my campaign. After stumbling across this blog, you've awakened a 'simulationist' obsession I never knew I had.

Assuming that relatively isolated cultures progress at varying speeds, I would think it could be possible for explorer and pioneer-PCs to find a functioning bronze-heavy society.

This isn't related to today's post, but do you have any plans to address the costs of goods? My apologies if you've already done so, but after reading much of your site I suspect the AD&D books to be wildly off on prices of goods, equipment, arms, and armor.

Zzarchov said...

The issue with bronze VS iron is often confused with bronze vs steel as steel would routinely appear when making iron (not intentionally but as a bonus due to accidental carbon impurities), so "strong iron" often references steel, even in the "iron age".

S. S., CFA said...

One other issue ... bronze doesn't hold an edge as well as iron or steel.

I'm not really into metalsmithing or metallurgy (more into cooking, actually ... and knives are where I get this info), but perhaps the difference is because iron is more brittle. Generally speaking, it seems like brittle often means a better edge (obsidian can be insanely sharp, but very very brittle ... likewise ceramics).

So, if brozne is harder to sharpen and/or keep sharp ... that would be an issue when you're knee-deep in the gore.

S. S., CFA said...

A comment to "R" on the prices of goods and equipment in AD&D...

They ARE wildly off historical examples ... but then, there were no dragons sitting on mountains of gold or vast piles of jewels lying in moldy tombs back in medieval France.

I think Gygax addressed this in the 1st edition Player's Handbook -- saying that the prices reflected an inflationary (or even hyper-inflationary) environment akin to what history happened in gold rush areas (like N.California, Alaska, Australia, etc.) when there was that huge influx of gold.

JB said...

I am not a metallurgist either, but my understanding is that iron, and its abundance, was known at the same time cultures were using bronze, but that bronze was less brittle (and thus more suitable to warfare) than iron. Steel replaced bronze (and ushered in the "iron age," I suppose more aptly called the "steel age") due to iron's commonality, once its forging was discovered (again, my understanding is that scarcity of tin was the weak link in the bronze equation, not any lack of utility, though steel is lighter).

I see old school D&D as very much a bronze age environment, complete with bronze age monsters (the classical monsters of myth). I've written before of using bronze as the "base metal" for D&D and having steel represent the lighter, sharper +1 arms and armor. But that's just me...I like ancient over medieval...
; )

Big McStrongmuscle said...

Speaking as an recently-graduated engineer with a (very) basic grounding in materials science:

In weaponry, the primary advantage of iron over bronze is its ability to bear an edge. Bronze can actually take more punishment than iron before breaking completely, but it deforms much more easily, which makes it an inferior material for cutting edges and (in most cases) for armor.

In general, metals that are more brittle - that is, likely to break under large amounts of stress - require more stress to deform than more malleable metals. Bronze, as the more malleable material, can actually bear more weight than iron before breaking. However, it does this in the same way a willow tree does: by bending. And worse, a lot more of this bend is what us technical types call "inelastic deformation". That is to say, the bend doesn't just stretch the chemical bonds holding the metal together, it breaks them, making the deformation permanent and the metal much weaker to boot.

Plus, since bronze's threshold for deformation is much lower than iron's, when the two metals clash, bronze will invariably be the one that nicks or dents first. If you repeatedly block a bronze blade with an iron shield, your enemy will soon find himself holding a bronze club. And while a bronze breastplate is still some protection against an iron sword, by the time you are done, it will probably be very thoroughly bent and dented to the point where you have trouble breathing.

The inability of bronze to hold an edge is why the Bronze Age Greeks employed short thrusting swords rather then big chopping blades, and also why they generally preffered to use spears. Points are considerably easier to hold than edges, since the smaller surface area can handle a little more blunting before becoming useless. You may note that it was not until the advent of the Iron Age that soldiers made the transition to the cutting swords that the average D&D player is probably more familiar with.

Although, yeah. Iron is also way easier to find than copper and tin.

Michael Giffin said...

When speaking of bronze, it is important to pay attention to what is alloyed into the copper to make the bronze. You pointed out that tin was a replacement for arsenic long after bronze itself was a known Factor.

In looking into modern bronze Alloys I have come across the idea of aluminum bronze. Replacing the tin in a traditional bronze mixture with aluminum leads to an exceptionally strong and lightweight bronze far superior to steel of the same volume. And what is aluminum? An extremely lightweight high-tensile metal that can only be produced through certain difficult to prepare processes either chemical or electrical. In fantasy settings what is mithril? A silvery lightweight metal with a very high tensile strength that can only be produced by certain processes either alchemical or magical. In one of my games an ancient and secretive order of knights use mithril bronze armor and weapons. The armor itself is coin mail. Functionally the same as scale mail. But it's Unique construction and metallurgic properties renders it a light armor instead of medium and easy to move around in. Nobody else in the setting knows how this armor is forged. It is a closely guarded Secret.

Alexis Smolensk said...

That strikes me as an excellent way to envision the forging of mithril.