Copper Casting In Ancient America

Did the ancient Americans know how to smelt and cast copper? Arlington Mallery certainly thought so. He dedicated many years of his life to this research, and excavated many
ancient furnaces in the eastern US, but unfortunately the professional archaeologists were not interested.
And yet, some professional metallurgists did agree with his results.
Dr. Earle E. Caley, was a professor of chemistry at The Ohio State University. He reviewed the metallurgical content of "Lost America", by Mallery, and endorsed some of his results. Caley in 1953 was already a published archaeo-metallurgist, and later became noted for his studies of the pre-Inca Moche Indians of Peru, who smelted copper from the ore beginning in 200 AD.
[quote]
Copper Casting In Ancient America? http://www.iwaynet.net/~wdc/copper.htm
To my knowledge, Caley never reversed his positive evaluation of Mallery's evidence of copper melting and casting by North America's pre-Columbian Indians. It is really strange that no American archaeo-metallurgists have seen fit to follow up on this.
[unquote]
Nothing strange at all, in my view. This is called politics.
According to Mallery, over 100,000 copper objects, such as tools and ornaments, have been found in North America. But I guess this wasn't enough to change the established opinion that the Indians weren't sophisticated enough to do such things.
So today, our archaeology textbooks still read that the North American Indians did not know how to melt and cast copper.
Regards,
Yuri.
Yuri Kuchinsky in Toronto -=O=- http://www.trends.ca/~yuku
It is a far, far better thing to have a firm anchor in nonsense than to put out on the troubled seas of thought -=O=- John K. Galbraith
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I don't think you've identified the controversy, Yuri. The question is whether the Indians worked only native copper (free, metallic copper, akin to native iron, or bog iron) or if they smelted it from ore.
It's well known that they worked native copper. They were doing it when the white man arrived in North America. That's what the town of Yellowknife, NWT is named for.
For that matter, the Indians in several areas, such as here in NJ, also worked bog iron. But it was such a rare thing that they can hardly be said to have leapt into the iron age.
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Thanks for your reply, Ed.
Ed Huntress wrote:

Well, they could have also smelted native copper, in order to make casts.

Yes.
Could you please provide more details of this?

How rare was it (working bog iron)? Have some iron smelters been identified in your area?
All the best,
Yuri.
Yuri Kuchinsky in Toronto -=O=- http://www.trends.ca/~yuku
It is a far, far better thing to have a firm anchor in nonsense than to put out on the troubled seas of thought -=O=- John K. Galbraith
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This is interesting to me because I have on three or four occassions tried to cast copper with little success. The casting is always full of holes. I assumed some gas was taken in in the liquid phase and outgassed as the phase changed back to solid. It would seem that a flux of some sort is needed but I didn't go any further with it. How is copper cast without this problem? Rick
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.

akin
The term "smelt" usually refers to chemically reducing a metal from its ore (although the use is not entirely uniform -- sometimes it just means the same thing as "melt." But in reference to metals and metal ores, it usually means chemically reducing at high temperatures). They could have melted native copper or any metallic copper without much trouble, using wood charcoal and a blast of air to generate the high temperatures required, but whether they smelted it from ore is a question.
I don't know about ancient methods for smelting copper. You probably could find info about it on the web.
Someone in this thread says he had difficulty melting and casting copper; it came out porous. That's the basic problem. It has such an affinity for oxygen that it requires special methods to cast it without gaining porosity.

NWT
I'm afraid I don't have any. It's something I remember from state history classes, decades ago. "Mining" bog iron (actually, scrounging for lumps of the stuff) was the earliest real industry in the southern part of New Jersey. The bogs in the NJ Pine Barrens contain one of the largest concentrations of bog iron in N.A. What I recall is that the Indians there had made some objects from it in pre-colonial days. There also was some Indian use of meteoric iron, if I recall correctly. That was done all over the world, before the methods for smelting it became widespread. Of course, meteoric iron is very rare.
Iron is relatively easy to smelt, combining charcoal and iron ore (iron oxide). When you mix the two and heat them up to some temperature above 2200 deg. F or so in an oxygen-lean environment, the carbon produces CO and the CO combines with the iron in iron oxide to form CO2, leaving metallic iron behind. That kind of smelting was discovered thousands of years ago in various parts of the world, such as India. As I said, though, I don' t know what the reaction is for copper ore, nor how they smelted it. Today, it's a chemical-and-electric process.

There is a fair amount of information about it on the web. I didn't check out any sites, but searching Google for Bog Iron Indians produced over 4,000 hits.
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Eh, they say the memory is the second thing to go. I'd better clear up something about bog iron.
Bog iron actually is a highly concentrated iron ore. Some sources say that free-iron (native iron) is not found in bog iron. Others say that small lumps of native iron have been found in bog iron deposits. I have seen one lump of native iron about the size of a soccer ball, allegedly found in a bog iron deposit, in a museum years ago.
Most sources say that almost all native iron is actually meteoric iron, except for a few iron-nickel deposits in the US.
Sorry, I don't have time to track it down further. To complicate matters, it appears to be true that some bog iron is so concentrated that it doesn't need much or any reduction to free the metallic iron in it. It can just be melted out, more or less, although those sources don't seem to be very technically astute. Just guessing here, but I'll bet they mixed some charcoal in with the bog iron to generate enough heat, and that also supplied some CO.
Or maybe not. I do recall a story from south Jersey that iron of such purity was found in the 'Barrens that blacksmiths could just heat it in their forges and forge it on an anvil. It would be interesting to track down the stories but it seems to be such a mix of history, technology, and ancient myths that it would take some real work.
Ed Huntress
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it
purity
That's not all stories. Concrete evidence is presented in [oh no is she going to put her pet-book forward again :-) YES I am] Iron and Man In Pre Historic Sweden. In academic articles such as:
Calissendorff Karin, Linquistic Evidence for Early Iron Production, ur Iron and man in Prehistoric Sweden, and Holmqvist Wilhelm, The first Iron in Sweden, ur Iron and Man in Prehistoric Sweden and Serning Inga, Prehistoric Iron Production, ur Iron and Man i Prehistoric Sweden, and Thlin-Bergman Lena, Blacksmithing in Prehistoric Sweden,ur Iron and man in Prehistoric Sweden,
as well as all the other essays you can find the information thought not to exist from real life analyses and studies.
Inger E

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the
ancient
<snip bibliography>

to
Thanks, Inger. Do those sources say that the ancient Swedes found native iron in bogs? I do recall that the Swedes were *smelting* bog iron ore in very early times, but maybe you know if they had native iron, as well?
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Pre
I don't recall that. Have to check my notebooks.
Inger E

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On Tue, 25 May 2004 07:38:52 GMT, "Ed Huntress"

Google "bog iron" (with the quotes) will give you some interesting references on this topic. One article discusses the Swedes and another the action on Long Island by the colonists. I did not see a mention of the native Americans working with bog iron.
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I'm not even sure how much smelting was necessary given that the copper on Isle Royale in Michigan was extremely pure.
Duncan Craig
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There is native copper in Michigan's UP, and that doesn't require smelting. However, if you're going to cast it, you still have some problems. I don't know how the ancients solved those, either.
Ed Huntress
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Ed Huntress wrote:

Ed,
    There isn't much evidence to say that 'the ancients' in the Lake Superior region had any trouble working the pure native copper without melting it or casting it. OTOH, there is what I consider to be convincing evidence that Native Americans of that region were sophisticated in the manufacture of tools and ornaments from copper by working it cold, or by heating it below its melting point.
    The ancients almost certainly solved the problem by ignoring it.
Tom McDonald
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smelting.
don't
Not according to some authorities, and this is the crux of the controversy. There is some x-ray evidence of casting in the case of some Indian artifacts from the region:
http://www.iwaynet.net/~wdc/copper.htm
Ed Huntress
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Ed Huntress wrote:

Ed,
    Can you tell us what one should expect to find in the archaeological record if copper casting were to have occurred? The evidence for the use of copper in this area goes back at least several millenia BC (I've heard up to 7,000 ybp), and occurs early on in pre-ceramic contexts.
    How familiar are you with the metallurgy of copper, especially in castings? (There was no need to smelt copper from ore in that area.) Also, how familiar are you with the technique of xeroradiography in metallurgy? I don't know enough about it to tell whether the voids shown are really the result of casting, or might have resulted from folding (for the linear voids), etc.?
Tom McDonald
    
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controversy.
artifacts
'Don't know much about archaelogical records, Tom. I would expect to find some molds (apparently some have been found). Beyond that, I can't think of anything that would be unique about it. Of course, that's excepting the objects themselves, which provide some evidence.

I'm rusty, if that applies to copper. <g> I used to be materials editor for _American Machinist_. At one time, I knew the metallurgy of it fairly well, as well as the average metals tech, including the range of copper alloys. But not now. I have to go look up anything that I want to know.

Again, once upon a time... I've written a few quality-assurance articles about the use of x-ray inspection of castings, but I don't remember enough to get into any details.

As far as I recall, native copper tends to be very homogeneous, except for large mineral inclusions, and often is very pure. The kinds of bubbles that occur in casting (which are still a problem today) are probably recognizable by any good inspection technologist, let alone a degreed metallurgist. And there are several of the latter, referred to in a couple of messages in this thread, who appear to be certain that they're looking at the result of melting under atmospheric pressure -- a condition that tends to produce bubbles in copper castings, and which is well-known in the foundry industry.
But this is all second-hand. I respect the opinions of some of the authorities quoted in this thread, and I know from first-hand experience that x-ray inspection of castings can tell an expert quite a lot about the condition and origins of the material.
In any case, I hope we're not still confusing two distinct things that have crept into this discussion: smelting from ore, versus melting metal for casting. It would take some convincing to prove that Native Americans were smelting metal ores. As I said, I don't know anything about ancient copper smelting methods, but I'd want to know more than sketchy evidence and speculation before I'd believe it.
On the other hand, that they cast copper wouldn't suprise me a bit. You or I could do it on our charcoal grills, with a hair dryer for blast and a steel cup for a crucible. It would be crap, but it would melt copper. <g>
Ed Huntress
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Ed Huntress wrote:

<snip>
Ed,
    In what would the copper be melted? What would ceramics used as crucibles look like, in terms of firing, shape and type of clay used? Could copper be melted over an open fire with some method of adding oxygen (fanning, blowing, ?). It takes ca. 1100 C or ca. 2000 F to melt copper. Or would it take some sort of enclosure, which should leave at least some vitrified material behind? These things should show up in the archaeological record; but they don't, not in the Upper Great Lakes area.
<snip>

    Yes, I think this seems to be, to this untrained eye, the likeliest way forward in examining the possibility of copper being cast in the Upper Great Lakes area. Of course, I'd like to know the limits of such testing, and whether there are any ways to produce cast-like xeroradiographs without the material having been melted and cast. I'd also like to know what one would look for with a SEM, or other techniques, to differentiate cast vs hammered copper.

    AFAIK there is no suggestion that Native Americans in the Great Lakes area, upper or lower, smelted copper. It would be coals to Newcastle, when the native copper was already at least 99% pure. There is some discussion about possible smelting of iron; but that's another discussion.

         Don't tease me, Ed :-). Dish the dirt on casting copper as the Indians of 5000 ybp might have done it. (See my questions above.)
Tom McDonald

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or I

steel
Aack! You want a pure hypothesis; sheer speculation? I don't usually do that. <g>
However, just this once...
For five millennia BCE, the Mediterranean cultures often used chipped-stone molds to cast copper and bronze axe heads and knife blades, so I'll assume the Native Americans could have done the same.
The melting point of copper (1984 deg. F) can be achieved with natural-draft tuyeres and wood charcoal (iron is still smelted and melted that way, at higher temps), so I'll assume that, too.
I'm going to assume further that the NA's primary reason for melting copper was to consolidate small pieces, so I'm visualizing a stone cupola-type furnace -- a cylinder of stone, maybe twice as tall as it is wide, with some clay to hold the stones together. This is similar to the ancient Cypriot copper-smelting furnaces, which ran at somewhat higher temps to reduce copper ore. (Yes, I just had to look that all up.) 2000 deg. F doesn't require an especially refractory clay, so local clay probably would have done the job.
A "natural-draft tuyere" in a stone cupola-type furnace is nothing more than a few stones that can be removed near the bottom. <g>
Put the one-piece, open stone mold face-up on the bottom, with some clay arranged like a funnel to feed molten copper into the mold. Stack layers of small copper pieces and charcoal on top -- say, three feet high. Toss in some iron ore for flux, if you're a high-tech Indian, light the sucker from the bottom, and stand back. Bring marshmallows or hot dogs if you have them. Any dog will do in a pinch. It's boring waiting for these things to burn down, and you'll get hungry.
'Next day, dig out your axe head or knife blade. Don't burn your fingers.
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Just about anything, I imagine. Not many clays melt at that temperature. A good ball or fire clay will certainly work well.

I've seen a documentary (on an ancient ice mummy, Utzi is the phoenetic spelling) where they filmed some aboriginal (for lack of a better term) people melting copper with about a foot of snow around. (The warmpth of the operation is very welcome. :) They had a nice charcoal fire going with some clay tuyeres leading into it. Some leather bellows fed the air. A hollowed stone or clay crucible held the metal which was then poured in a clay split mold for the axe head they were making.

Preferred for sure, not sure they would've thought of that though.

I actually brought a piece of my own cast bronze to the local college's SEM and had the prof scan it... didn't look too remarkable (crystal structure, etc.) on any surface, at least at the scale he scanned it.
Tim (sitting in a Residence Inn in Fresno, on vacation til friday or so :D )
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On 26 May 2004 17:54:43 -0700, snipped-for-privacy@charter.net (Tim) wrote:

Although they may not melt, many clays will crack or spall at the temperature required to melt copper. Just learning how to make a crucible which will survive the process would have been a task in itself.

Eric Stevens
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