Copper Casting In America (Trevelyan)

What's that???

"3,000-year-old metallurgical tradition,"?

Golly gee, whoever had written this blurb doesn't even know that this metallurgical tradition is actually 5000-year-old!

What a blooper!

Page 9 of Trevelyan's own book states,

"The Old Copper Culture was a Middle to Late Archaic development that lasted from about 3000-1000 BC, and was focused primarily in upper Great Lakes region."

This blurb is found in a few places on the Net, for example at,

University Press of Kentucky

So this seems like a standard blurb.

What a bunch of turkeys... Their ignorance seems infinite.

Yuri.

Yuri,

I noticed that, too. However, the blurb isn't the book. From the looks of things, the blooper was made by the person who wrote the blurb, not Ms. Trevelyan.

This seems to be correct, although I would have chosen to call it the 'Old Copper Complex'.

Might could be. The blurb is wrong; Trevelyan's text is correct.

Maybe. But you haven't demonstrated either.

But I do thank you for pointing this book out to me.

Perhaps you could show me some of this evidence (other than the Connor web site or the Mallery book; I can always read the former, and have requested the latter by ILL).

Why would it be mentioned? Her book is on copper usage, (apparently more wrt its usage as art and ceremonial usage), and most of Mallery's book is about iron. In any case, Trevelyan would most likely have wanted primary sources on the metallurgy, not a book like Mallery's which quotes them.

Have you read the book? Or are you judging it by a non-technical blurb and a few selected quotations? If the former, good on ya; if the latter, then quityerbitchin until you have.

Tom McDonald

Bizarre for you to be correct, but yeah, you certainly are dumbing down the subject quite considerably.

Realize that casting is primarily a technique used for cheap mass produced items. It allows relatively low skilled workers to produce large numbers of relatively complex identical items. Cold working is a much more challenging, and artistically unique, way to produce intricate copper ceremonial items. The smith has to have a higher level of skill than the foundryman to produce equally complex work.

Given that, it seems to me that your claims of bigotry by a art historian are unfounded. If anything, the idea that the art objects were produced by cold work makes them even more impressive examples of the skill of the worker than if they were mere castings.

But that said, casting pure copper is a bitch. Porosity is the enemy, even for modern copper founders. They charge a hefty premium for low porosity castings. Alloying the copper to make bronze improves matters *enormously*, and production of such alloys was a huge technological leap forward for the casting industry.

*If* the Native Americans of millenia past made the technological leap of producing bronze alloy, it would be a significant achievement (as it was when Old World artisans did it). But I've seen no evidence produced in this thread that the ancient Native Americans made such a technological leap forward.

The artifacts described appear to all be relatively pure native copper. As such, the *intelligent* way of working the material would have been smithing rather than casting. So if the motive were to make ancient Native Americans appear stupid, then claiming that they used open casting techniques would be the method of choice to do so. Now ask yourself which side of the argument is making that claim.

Gary

...

The evidence is in the Mallery book, and I've already quoted it here.

Because it's relevant.

Non sequitur.

Yuri.

Yuri Kuchinsky -=O=-

A great many people think they are thinking when they are merely rearranging their prejudices -=O=- William James

Yes, Gary, but an intelligent metalworker will use the technique that is most appropriate for the situation.

It would be rather impressive if the worker knew how to use a variety of techniques.

The Native Americans of millennia past certainly knew how to produce bronze alloys. There's plenty of evidence of this in S America, for example, and in Mexico.

It's also an interesting subject if the ancient Native Americans of the Great Lakes area knew how to produce bronze alloys. I don't exclude this possibility but, at this time, the evidence seems to be lacking. Nobody has investigated this possibility before, no doubt because of a racist bias in N American archaeology.

Not always. See above.

Best regards,

Yuri.

Yuri Kuchinsky -=O=-

-=O=- Toronto

But scientists, who ought to know Assure us that it must be so. Oh, let us never, never doubt What nobody is sure about. -- Hilaire Belloc

Yeah, she's definitely more racist than the white-god junkies.

[..]

"Show me where, except the evidence of it" statement by Tom. So, if one was to show another source than those he has excluded (which I have done a while ago already), then he could add that to the list of "except...", I presume!

[..]

[..]

Whilst there is little argument with that, it is still illogical to believe that casting wasn't done. Each maker of jewellery, ceremonial items would have ended up with "scraps" of copper. It is unlikely they would have simply been thrown away. The annealing of copper would bring it to melting temperature often enough for smaller thinner bits. It suggests a very likely occurrence that they did melt copper, if for no other reason than to make bigger pieces out of the small scraps and off-cuts. This they would again cold work another time.

IIRC silver is found in with copper deposits in the Great Lakes area and it has a melting point a bit lower lower than copper. It is likely they could have used a silver/copper alloy or "bronze". If the minerals co-exist then there is no need for "mixing", it is automatic as with arsenic/copper deposits.

You see, the thing is that cold working something doesn't require "technology", where melting/smelting does. It is the implied lack of technology where the suggested prejudices arise from.

If they did open atmospheric casting (and I'd strongly contend they didn't have the technology to do any other kind, nobody did until the latter half of the 19th century, and then only as a laboratory curiosity), the resulting copper wouldn't be suitable for cold work, too much porosity.

Note too that the annealing temperature of copper is *way* below the melting point. If they did melt parts of an object they were annealing, they were using grossly too much heat. In other words, it would be a mark of incompetence on their part if evidence of such melting were found.

If they did attempt to salvage copper scraps, they likely *hammer welded* them. That's done at temperatures below the melting point of copper, so porosity doesn't become as serious a problem.

You need to understand that copper behaves *differently* from silver, gold, or even iron. Those metals respond well to casting techniques. Nearly pure copper does not.

(Bronze is a different matter, of course, but there still has been no evidence presented of bronze artifacts from the locale and period under discussion in this thread.)

A quick search of the UNS database doesn't show any silver-copper binary alloy listed as suitable for casting. Nor is such a binary mixture called bronze.

The search did turn up "nickel silver" copper alloys suitable for casting, but the composition of those alloys *contains no silver*. They do contain large amounts of tin, nickel, and a bit of lead. All of the binary alloys of silver and copper listed are labeled as "wrought", meaning that they are suitable only for cold work.

The associated native copper and silver found in the Keweenaw Peninsula is known as "Halfbreed". It isn't even an alloy (solid solution). It consists of intertwined gross crystals of the two separate metals. It is difficult to produce an alloy of silver and copper in the absence of tin.

If you heat a sample of Halfbreed, the silver melts out before the copper reaches melting temperature, leaving a mass of copper with voids where the silver was. It does not produce bronze.

The presence of tin is usually, though not always (aluminum bronze being the primary exception), a prerequisite for a copper alloy to be called bronze. I'm unaware of any tin deposits in the UP of Michigan.

Note, an alloy of arsenic and copper was once called bronze too, but it is dangerous to produce, and exceedingly brittle in use. Old World artisans very quickly abandoned it. Again, no evidence of artifacts from the UP of Michigan composed of that alloy has been presented.

Hmph! You might remember that one of the newsgroups where this thread is appearing is the *metalworking* group. Most of the members are machinists, either by vocation or avocation. In other words, their primary occupation is working of metals at temperatures below the melting point. They would *strongly* object to the notion that casting should be the signature mark of metalworking technology.

Most of the more advanced technological working of metal is done cold, or at least at temperatures below the melting point of the metal. That's *particularly* true for pure copper. Most of the more astute members would never even consider casting as a viable method for producing pure copper objects.

Note that I am not insisting that no copper casting industry existed in the UP of Michigan in pre-Columbian times. At least one radiograph I've seen seems to indicate copper which had been melted in atmosphere at some point. But what I am saying here is that atmospheric copper casting is a particularly unintelligent way of utilizing the pure metal when the alternative of lower temperature smithing is available.

So the apparent fact that most of the artifacts found show evidence that they were smithed rather than cast clearly indicates that the Native Americans were sophisticated in the working of the copper available to them. Insisting that they cast the objects instead would be an attempt to show that the workers were *not* sophisticated.

A very important indicator of technological sophistication is knowing how to choose the appropriate method to work with a particular material. In this case, the technologically appropriate method is

*not* casting. So if your objective is to minimize the technical prowess of the Native Americans, you'd be in the camp pushing for copper casting. Casting dumb, smithing smart.

(Again I must point out that bronze is a different matter, but no evidence has been presented to support the production of bronze in the locale and time under discussion.)

Gary

Indeed! And atmospheric casting of pure native copper is *never* the most appropriate method. Its use would be a clear indicator of the lack of sophistication of the metalworking technology of the people involved.

It is even more impressive when the worker knows enough to choose the most appropriate technique for the material being worked. In the case of nearly pure native copper, that technique is *not* casting.

Gary

[snip]

But casting and/or smithing (depending on the materials at hand) is more smart than just smithing.

Yuri.

Yuri Kuchinsky -=O=-

Students achieving Oneness will move on to Twoness.

--- W. Allen

Hmm... I wonder. Is there anyone besides yourself who thinks so?

Yuri.

Yuri Kuchinsky -=O=-

Students achieving Oneness will move on to Twoness.

--- W. Allen

Have you personally tried casting pure copper??? Any metal for that matter?

I haven't tried copper but I imagine it isn't pretty. Unfortunately my stock is contaminated with zinc, as I throw pennies (5% Zn) in with the pure copper (wire, etc.) pile. ;)

Tim

-- "I've got more trophies than Wayne Gretsky and the Pope combined!" - Homer Simpson Website @

Well, I for for one, while I haven't tried to cast pure copper, I did play around with melting pennies and tin from my dad's chemistry storage to get a nice bronze Stafforshire Knot. I have cast silver (although, per Inger, I don't know which Indian tribe mined it:-)). Indeed the silver belt buckle and bracelet I am wearing at the present moment I cast in tufa, ca. 1972.

Yes, I have cast metal. Have You?

tk

"Tim Williams" skrev i meddelandet news: snipped-for-privacy@corp.supernews.com...

I have tried copper long ago. When I was the only girl in 7th grade asking to have metal-handicraft instead of the obligatory needlework for girls that was one of the thing I had to learn, I also had to learn welding and of course forging. I didn't do it much only 3 hours/week for three years. Anyhow I can see your point Tim, but I don't agree.

Inger E

True, when the material isn't pure copper. Bronze casts very nicely, for example, as do gold, silver, iron, etc. But pure copper doesn't. As Key to Metals says, "Pure copper is extremely difficult to cast as well as being prone to surface cracking, porosity problems, and to the formation of internal cavities."

Commercially, pure copper is melted and cast using a furnace that is inert gas purged, a crushed graphite cover is floated over the melt, and when the melt reaches 1250 C, a small amount of calcium boride or lithium metal is injected into the melt to act as a deoxidizer.

While silcon bronze can be successfully gravity cast in a sand mold, pure copper cannot. Pure copper needs to be pressure molded, either via injection or centrifugal casting methods. The molten metal should not be exposed to air during the casting process.

Casting pure copper is a highly sophisticated process of the modern industrial age. The techniques to do it successfully were only developed near the end of the 19th century when the demand for high purity copper castings for the electrical industry drove research and development. It is still difficult and expensive enough to do that aluminum, brass, or bronze is substituted for pure copper wherever it is practical to do so in electrical equipment.

Gary

Yuri has me killfiled so may not see this, but I am fed up with his going on about 'smart' and 'dumbing down'. It takes more than intelligence to develop technologies, and the lack of a technology does not mean that a group of people are 'dumb'. To say that Native Americans did not develop electricity, nuclear power, or various types of metalworking does *not* mean that they are dumb. And it doesn't make the person making the statement racist.

This is basically just Yuri's need to cast nasturtiums at scholars, this time archaeologists. He does the same thing with Biblical scholars in other newsgroups.

Doug

I picked up on the fact that he was more interested in axe grinding than casting.

Gary