The archaeologist quoted, Perino, wrote that the possibility of casting should be looked into. This is proper. He mentioned two "crucible-like" vessels, but I didn't see any reference to a possible furnace, or to studies of the inside of the vessels for traces left by molten copper.
Perino says that there were no copper scraps found at the site. Copper scraps would have been valuable materials, and certainly would have been re-used. However, there's no reason that I can see that they would have to have been melted down for scrap. Copper scraps can, IIRC, be hammered together to usable sizes without melting. Perhaps some kind folks from the metalworking group can give us guidance here.
There certainly are some intriguing hints regarding casting copper. But to my mind, there isn't anything like a strong case for it, and certainly no strong case for it being wide-spread in the upper Midwest of the US and the Great Lakes areas of Canada.
'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. 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.
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.
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.)
Aack! You want a pure hypothesis; sheer speculation? I don't usually do that.
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.
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.
All I was doing was providing a reference to possible crucibles for Tom Kavanagh's benefit. After all, when he asked me for one a couple of days ago I said I didn't have any.
If the analyses cited by Mallery can be confirmed today then the evidence for copper casting is iron-clad (or should it be copper-clad?). Cast artifacts exist - period. You can't have a stronger case than the finished product.
No, the they I was referring to were merely hypothetical ancients.
I do know some about pouring copper, though. And I can tell you that even 1 % is a lot when talking about an alloy's properties.
Back in college, I worked on a project recreating the Japanese metalworking process called Mokume gane.
In the furtherance of this, we poured ingots of copper alloys ranging from electrolytic tough pitch scrap to copper with 2-25% silver, copper with .5-5% gold and copper with .5% arsenic. All with equipment no more advanced than a coal forge, a crucible and an ingot mold.
None of the alloys displayed the spitting and out gassing that the tough pitch did.
Next the ingots were rolled out to about 1/4 of their original thickness.
Although the tough pitch tended to blister( even that didn't start until it was reduced about 30%), problems with the others had more to do with technique than the properties of the copper,and for the most part they rolled fine.
These were then laminated together in the forge with tough pitch copper (manufactured sheet) and whole block reduced to approx. 1/30th of the blocks height.
Some tearing and blisters occurred but these had more to do with the lamination process and, once that process was worked out, it was the exception rather than the rule.
My point is that the casting of copper is difficult compared to casting silicon bronze, but it is not impossible.
Did they cast copper in the UP? I don't know.
Could they melt copper? Any nitwit with enough wood and a stiff breeze can melt copper.
Could they have cast copper? This is not a stretch. We tend to think of them as though they were retarded, but they were primitive, not stupid. If all you want is a bar of copper, suitable for an axe head that is better than a rock, you probably won't have a lot of trouble, regardless of your alloy.
Did they alloy it? Again, I don't know, but it is not that tough.
Did they smelt copper from base ores? I doubt it. Only pyrites and other sulfides are simple to reduce in fire and even they require fairly complicated and energy intensive processes.
Given that the Americas had ample supplies of native copper for it's population, I think the peoples without native copper would have been better served developing trade routes than developing arcane alchemical processes.
"Paul K. Dickman" says in news: firstname.lastname@example.org:
That was kind of my question, and they already had crucibles, grinding mortars used for grinding corn. All that really needed to be added is a mean of keeping the mortar upright (a pile of rocks) and something to handle the mortar stone with after the copper was molten (Such as a wet forked branch).
Oaxaca was the big copper culture in the new world. A small amount of research on them will reveal how they collected the raw materials and refined it. I also beleive there is a cultural connection between the carribean industries and the SE U.S. industries.
Oh-oh, if it is listed ate Doug's web pages, then it is certain to be questionable. One needs not read more than the so called "Abstract" to get the distinct smell of revisionism. Yes I have seen this paper before and it is bogus.