From: http://www.the-orb.net/encyclop/culture/scitech/iron_steel.html
[quote]This allows the iron atoms to combine into a mass of metal. Rust goes in; iron comes out…

The smelting furnace has two tools to bring about this transformation: heat and carbon. Smelters, like all furnaces, burn carbon fuels to produce heat; that much is obvious. But burning is never complete, and the hot gases within a smelter are rich in carbon that is chemically active. Hot carbon has a strong affinity for oxygen, and the oxygen atoms are literally stripped away from the iron by the gaseous carbon. Left without any chemical partners, the iron atoms form a mass of nearly pure metal…[/quote]

(sorry if that quote code doesn’t work - learning the formatting codes here)

As far as I can tell, and I have been poking abouts quite a bit on this, there is no real decrease in quality as metal rusts.

The quality of an ore is primarily measured by how much metal you can get out of it, versus how much effort it takes to get it out. The more a block of iron rusts, the less iron there is to get out of it, so the less its quality as an ore.

First, it seems that the Chinese blastfurnaces ran on charcoal.

You wrote:
The problem is that the more rusted the metal becomes, the lower its quality as an ore.

As far as I can tell, and I have been poking abouts quite a bit on this, there is no real decrease in quality as metal rusts. In fact, from what I’ve read, rusting, the process of oxidizing iron molecules, can actually both take the iron out of an alloy or impurities (since the iron rusts seperately and at different rates from other elements).

Also, from what I’ve read, most iron can be purified (even sulfer can be pulled from it) with nothing more complicated than limestone (and was done, before industrial tech or coal), at charcoal temperatures. You just need the know how and the time.

Also, it seemsJ that bog iron is Fe(III) - the same as rust. However, bog iron contains silicates that form a protective glasslike sheen on forged products protecting them from rust.

The limiting factors on iron seem to be primarily the knowledge of how to work it. It is a complicated metal, and it is not straight forward to work.

Certainly iron will never again be used in such a casual way as it is now, as industrial charcoal production and hammering blacksmiths will not be around in more simple societies. But it seems very likely to me that iron tools aren’t going anywhere.

I would also like to throw out that I think there is a lot left to learn about iron metalurgy. There are several historical iron artifacts that modern metallurgists don’t quite know how to replicate. Iron working was a continually developing “magic” up until the industrial revolution, when all of the art left it, and was replaced by high energy “blunt force” reactions.

Of course, the scavenger culture will be affected by the fact that their supply will be rusting through. After a few decades, the supply of ferrous metals available to scavengers will be half rust. Rust is iron oxide, just like iron ore, so it is possible to smelt rust just like an ore. The problem is that the more rusted the metal becomes, the lower its quality as an ore. In general, rusted metal is poorer quality than any mined ore. In the immediate aftermath, scavenged metals will be far more economic than mined metals, but there will be little recourse for casting them. That shouldn’t matter too much to the scavengers; there’s still enough that can be done with heated and reworked scavenged metals without actually melting it down and recasting it to satisfy most of their needs. After a few decades, as the scavenged ferrous metals become more and more rusted, the EROEI of metalworking will begin to diminish as it becomes harder and harder to make poorer and poorer metal weapons and tools.

Finally, most of the iron available to a scavenger are alloys, which generally can’t be worked in a charcoal fire. Those require much higher temperatures.

On a related note, a question for Jason: Is there anyway to happily (environmentally and socially) have any complexity above paleolithic?

My intuition is “no,” with the caveat that the complexity of the Paleolithic was still sufficient for all manner of wondrous things, and that while we may be bound to that level of overall complexity, no one’s said how we need to apportion that complexity.

Its a good site on the smelting of iron.
A few main points from it, and extrapolated from it:
1) Smelting to increase or decrease the carbon quantity in iron is possible with charcoal, as is forging.

2) Removing slag from iron fairly straight forward, though it takes a lot of muscle energy.

3) Rust has nothing in it that would prevent it from being smelted into quality iron, given access to enough iron rust (which cities will certainly provide), enough charcoal, and enough fresh boar meat.

4) At no stage do you need to melt raw iron rust or ore (though you can melt carbonized iron, which requires a lower temperature).

It seems to me to be possbile that the amount of iron available to humans could remain at a somewhat steady level after the fall of civ, slowly decreased by inevitable loss, slowly increased by new finds of ore or bog iron.

There are two issues:
1) Certain modern alloys. No idea if modern alloys can be resmelted with charcoal. This would limit, though not elminiate the quantity and quality of avaialbe iron.

2) Energy throughput. Especially working with rust, you need a lot of energy, both wood and muscle, to produce iron in quantity.

On a related note, a question for Jason: Is there anyway to happily (environmentally and socially) have any complexity above paleolithic?

True. But pople didn’t undetstand the long-term implications of farming marginal lands or cutting down trees on soil. Easter Islanders had less excuse since the effects of deforestation in such a limited area would have been more obvious. Unconstrained tribal competition or modern capitalism encourages such short-term thinking.

It is possible for communities to sustain collective long-term projects in which everyone has a responsibility and shirkers or freeloaders are punished. For example the Dutch have been building and maintaining their dykes since roman times, even though lack of maintenance must take decades to have effects. I think the key is that the effects of action or inaction must be easily detected or visible and the long-term consequences of the policy are clear to everyone.

If soil quality and tree health were regularly measured and published for each region and recognised as valuable by the community, I believe local pride and regional competition would ensure sustainable practices were followed. It is easy to become disillusioned in modern society, but communities with high social capital have much more collective power to enforce standards.

Toby

Some things metals are particularily good at, but there are alternatives for most uses. I believe a societies’ level of complexity and sophistication is determined more by its literacy and the level of knowledge than use of metal.

All facets of complexity are interrelated, so Liebig’s Law of the Minimum applies. So complexity can only proceed as far as the most scarce resource allows. Otherwise, we’d need to base all this on the premise that Neolithic kingdoms were simpler because they weren’t as smart as we are today.

Iron ploughs for intensive farming are the only obvious metallurgic dependency here. It is interesting that recent work in permaculture shows the most productive agriculture is based on perennial plants, not annuals which requires ploughing the land. Just because we lived a certain way before the Iron Age, doesn’t mean we have to live that way after it ends.

That’s really the major limitation, though. Without an iron plow, you’re stuck with stone plows, which break more often. That means smaller fields, less economy of scale, and so forth. That means smaller harvests, which means smaller population. Without metals, your storage facilities are smaller since you’re stuck at the scale of purely wooden buildings, stonework has to be much simpler, and all of this greatly reduces the benefits of hierarchy while doing little to alleviate its cost.

But as for permaculture, we’ve discussed this extensively elsewhere. Permaculture doesn’t scale up the way agriculture does. It’s far more efficient, but its absolute yield is smaller. That absolute yield is really all that matters if you’re worried about maintaining hierarchical domination systems.

I dont think it’s complexity per se that uses energy and wastes resources. Many specialisations actually save energy/resources because they improve efficiency (with the cost of greater coordination). It’s Heirarchy, with unproductive layers of people, that wastes (human and natural) resources. If we can organise specialisation without heirarchy we would get the benefits of both worlds.

Complexity has a benefit, and it has a cost. It’s subject to diminishing returns. Specialization can be more efficient, unless you take it too far–then you get into diminishing returns. So even without hierarchy, there’s a balance to be maintained.

You point out metalworking has caused deforestation in the past. The question is whether a sustainable culture can include metalworking, or would that inevitably lead to deforestation and decline? I believe that if people are aware enough of land degradation and unsustainable practices they will act in the long-term interest.

Until the first opportunity arises where something that’s long-term catastrophic provides a short-term gain. You won’t eliminate personal ambition, but you can put it into a context where it’s constructive, rather than destructive. We had such a context for a million years; it was only recently that the context changed, and agriculture provided a means for people to gain short-term benefits at the cost of long-term catastrophe. In that setting, humans have proven incapable of appreciating long-term costs. It’s certainly understandable, but that’s also why I think any plan that relies on people being more forward-thinking in the future than they’ve been in the past is probably doomed from the outset.