I had been contacted by Gino Ferri of Survival in the Bush a (long) while back about a project involving First Nations copper tools. His desire was for a socketed style adze and a triangular axe blade. It should be noted that only vague descriptions of final shapes were given, so considerable background research had to be undertaken (beyond any technical production aspects).
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| 'Etowa Mounds' Copper Axes (note thickness!) |
Gino had provided me with a large pile of copper wire, which had previously had the insulation burned off. The intent here was to melt this down into plates or ingots, then use that material to form the replicas. I had mentioned I was in the process of working up a ‘medium’ scale, propane fired, furnace base for potential bronze casting use. In the end that project was long delayed (still not really not to the production level).
Ancient copper smelting (reduction from ore) was not so different than the furnaces I regularly use for bloomery iron making. If anything, the copper furnaces are smaller, although they do work in roughly the same temperature ranges (≠ 1100 C for copper) (1). So I remain fairly confident that a modified version of our standard clay cobb build (likely a shorter shaft) fuelled with charcoal will serve to melt the scrap into a rough ingot.
But this in itself will be its own learning sequence, and sure to consume almost as much in materials as the value of the scrap on hand (2)
Royal Ontario Museum
Medium: Copper
Geography: Bedford Park, Toronto, ON
Date: 4000-1000 CE
Period: Middle - Late Archaic period
Dimensions: (not given)
Object number: HD10407
ROM-1
Medium: Native copper
Geography: Ontario, Canada
Date: 3500-2500 BC
Period: Middle Archaic (6000-2500 BC)
Dimensions: 14.1 x 8.7 x 2.7 cm
Object number: NS3664
(Images and descriptions above taken from the ROM’S on line collections data)
Note the dating for the Archaic Period ranges from 8000 - 1000 BC. The objects are being only rough dated above, by style more than C-14.
Source copper is most likely from ‘Northern Great Lakes’, but you can see even the find locations are vague in these descriptions.
As (considerably) more digging on the internet was to show, hard information on early copper working by First Nations was to prove difficult to find…
Milwaukee Public Museum
“ The Old Copper Complex, also known as the Old Copper Culture, refers to the items made by early inhabitants of the Great Lakes region during a period that spans several thousand years and covers several thousand square miles. The most conclusive evidence suggests that native copper was utilized to produce a wide variety of tools beginning in the Middle Archaic period circa 4,000 BC. The vast majority of this evidence comes from dense concentrations of Old Copper finds in eastern Wisconsin. These copper tools cover a broad range of artifact types: axes, adzes, various forms of projectile points, knives, perforators, fishhooks, and harpoons. By about 1,500 BC, artifact forms began to shift from utilitarian objects to personal ornaments, which may reflect an increase in social stratification toward the Late Archaic and Early Woodland period (Pleger 2000). While copper continued to be used in North America up until European contact, it was only used in small amounts, primarily for symbolic ornaments.
To date, there is no convincing evidence that archaic populations of the Old Copper Complex smelted copper to pour into pre-made moulds (Martin 1999). Indeed, many copper artifacts show extreme uniformity and quality, indicating a high degree of technological specialization. This has led to speculation that Old Copper Complex artisans did in fact reach the level of smelting copper ore (Neiburger 1984). “
" The socketed spud is one of the more distinctive types of Old Copper artifacts. There is a large range in size and style of these artifacts, which may indicate both the time and place of their manufacture. They would have been hafted onto a wooden handle for increased accuracy and efficiency. Nevertheless, the function of these tools was primarily for woodcarving and possibly bark stripping.(Left to Right: 2144,
11616/1487, 11812/1571, 15728/4394, 15752/4947, 11622/1487, 2176, 11838/1571) "
" Axes and wedges are somewhat similar to chisels and celts in that they were probably often used for cutting wood and felling trees. Some of these artifacts show signs of being hammered on the butt end, perhaps for the purpose of splitting logs.(Left to Right: 11613/1487, 11614/1487, 11861/1571,
56432/22174, 11615/1487, 48414/15407, 2135, 11619/1487, 2234) "
Web page produced by University of Wisconsin-Milwaukee Anthropology and Museum Studies graduate student, Kevin M. Cullen in 2006
https://www.mpm.edu/research-collections/anthropology/online-collections-research/old-copper-culture/artifacts
Copper Culture
“ There is disagreement among the archeological community as to the time period to ascribe to the Old Copper Complex. Dates range from over 7000 years BP to 3000 years BP. The greatest disagreement seems to be over the beginning age of the Old Copper Complex. Carbon-14 testing of organic materials found with Old Copper Complex artifacts has established a date of at least 6000+ years BP. Carbon testing of wood remains found in sockets of artifacts in our own collection has produced dates as old as 5900+ years BP. Copper continued to be used into proto-historic times, long after the demise of the Old Copper Complex. Many of the copper artifacts from the Old Copper Complex differ from those of later manufacture, with many of the later artifacts being smaller, less utilitarian and more ornamental. “
“ The presence of gas bubbles on the surface of a few Copper Complex artifacts has been taken by some as evidence that these artifacts were in fact cast from molten copper. I have yet to see empirical evidence to support this copper casting hypothesis, no molds, no furnaces, no copper drippings and no slag as found with ancient or historic foundry operations and no partially completed artifacts with a casting sprue still in place. What has been shown to be true through modern day experimentation is that gas bubbles are rountinely formed in the pound/anneal process. Gas bubbles have been shown to form when copper is heated to a red-hot state in the annealing process due to gas expanding and attempting to be released. The vaporization of impurities in the copper can account for these bubbles. There would actually be more surface gas bubbles observed if it were not for the highly oxidized condition of many copper artifacts which has obliterated them. This phenomenon has been observed numerous times in the process of copper tools being fashioned by modern day artisans using the pound/anneal process. “
David H. Peterson
Two Harbors, Minnesota
(Independent Researcher)
https://copperculture.homestead.com/ManufacturingCopperImplements.html
Pulling together a number of descriptions this is what I could determine :
- ‘Native Copper’ in this part of North America, appears to have its primary geographical source as modern day northern Michigan, Wisconsin, Ontario around Sault Set Marie.
- Natural copper is also found as random sedimentary deposited ‘nuggets’ over a wider range, most likely due to ancient glaciation effects.
- During the earlier phase of the NA Archaic period, larger ‘plates’ of natural copper were available, likely as surface finds. (3) As time progressed, deposits were worked through at least limited surface mining, plus using fire to crack open larger rocks to break free hard to recover plates.
- The larger size of these plates allowed for cold hammering into correspondingly large objects, allowing for the creation of tools like wedge axes and socketed adze forms. (4)
- As time progressed, creation of these kind of large working (?) tools fades, objects of copper become much smaller and more decorative types. Taken together (method and object size changes) this certainly suggests dwindling raw materials as the reason.
- There is no archeological evidence, either on objects or as related tools and importantly lack of furnaces / slag that would indicate smelting or casting methods were ever used.
- There is structural evidence seen on objects of the annealing process being used. (5)
- There is no specific structural evidence seen on objects for use of forging (hot working).
My first step, once I had gathered the basic data was to determine just which of the limited artifact samples I was going to use as prototypes. Looking over what was available, I decided to chose two objects from the Milwaukee Museum collection :
11616/1487 and
56432/22174
In both cases I only had ‘top down’ images, so details like thickness or possible curvatures could only be guessed at.
I have in the past found that the best method to get a clear idea the actual sizes and proportions of artifact objects is to attempt to modify the source images to ‘life size’. This was to prove a bit of a WAG in this case, as even though the images had scales, there were no units indicated. There was also a bit of image processing via Photoshop to reduce to black and white and increase contrast.
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11616/1487 prototype to the left
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56432/22174 prototype centre
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My next problem was - just what materials did I actually have on hand? This would actually serve to modify the final sizes of the replicas, as much as scaling the images might.
As it turned out, I had one flat plate of copper, already partially forged, as well as a thick square block I considered about the correct size.
As discussed above, the original objects owe much of their shapes to their own starting materials, relatively thin plates. The artifacts would have been cold worked using hand held or possibly wood shafted stone hammers.
I most certainly ‘cheated’ in my own work! With access to a propane forge for easily controlled heating, I worked all my shaping working hot (6). Some of the initial profiling (especially taking the thick block to the blank for the adze) was done using my 75 lb air hammer. Also using a modern (c 1900) large, steel anvil, and modern steel hammers. I deliberately did my rough shaping using the slightly rounded surface of a crown hammer, finishing with my trusted round shaped main forging hammer. Both of these specifically chosen as I felt it unlikely square shaped hammers would have been used by the original copper workers here.
As the requirement was for an adze, a more specific design than the general ’spud’ shape seen in the artifacts, I curved the body of this tool more in keeping with later period iron woodworking tools I have made in the past. Each cutting edge was roughly drawn down to about 1/8 of an inch thick. I then (cheating again) used a belt sander to trim the mostly ragged edge to straight. The final edge (to about 1/16 inch) was then formed by cold hammering, which would also serve to at least slightly work harden this.
As a last step, the finished tools were cleaned to remove the dark oxide fire scale by socking in a salt + vinegar solution and scrubbing by hand.
All in all, I am extremely pleased with the final results.
The sizes are certainly within the range seen in the artifact samples, with the axe blade at about 3/8 inch thick. There might be some question on the curveture used for the adze, with certainly is more based on past experience than knowledge of the artifacts.
Notes :
1) “ The oldest (Old World) copper ornament dates back to around 8700 BC and it was found in the modern territories of Northern Iraq.
There is evidence for copper smelting and recovery through processing of malachite and azurite in different parts of the world dating back to 5000 BC. “
http://www.asarel.com/en/About/History/Copper_history.aspx
2) I had to dig around to get some numbers on the current value of scrap copper.
As industrial scrap, the current cost appears to be about $7.50 CDN per kilogram. Copper hit its peak cost about 8 years back, to about $12 per kg.
As a side note : Canadian pennies, before 1996, are 98% copper. It took about 420 pennies to make one kilogram weight.
3) The indication is that the natural copper being used here was formed as molten copper, formed and heated far underground, was forced into wide cracks in the surrounding rock matrix. Through the ages, natural processes (with a huge help via glaciers) forced up and eventually exposed or broke free these plate shapes.
4) The final weight of the two replicas seen here was 1700 gems, so about 850 gems each. These pieces are slightly smaller than the prototypes chosen, which themselves were on the larger end of the collected artifacts seen in reference images.
5) Copper, naturally quite soft, will ‘work harden’ as hammered. Eventually the metal will become hard and brittle enough that it can crack or break. For copper based materials, a worker can mitigate this effect by softening via annealing. In this case, the technique is heating the metal to a ‘blood red’ and quenching. The ideal practice is to finish a cutting edge by lightly hammering to thus work harden the final shape. Fine examination of the structural texture of objects shows this combination of methods having been used (thus understood by at least some artisans).
6) For any working smiths reading :
Copper is wonderful material to forge! Works in the orange ranges. As the melting point is in the 1100 C range, a propane forge is ideal. As the material cools, it merely becomes slightly (!) more rigid. (This unlike bronze, which depending on alloy, can become tragically brittle below forging temperature.)
Yes, as a material, is is roughly 10 x the cost of steel per lb. But on the other hand, experience has shown that an agressively forged copper object, despite the relative ease of the working, usually will command 10 x the finished selling price as well!
Re-cycled copper bus bar material is ideal.
