Science explains ancient copper artifacts

infinite monkey · 06-20-2011, 01:23 PM

Northwestern University researchers ditched many of their high-tech tools and turned to large stones, fire and some old-fashioned elbow grease to recreate techniques used by Native American coppersmiths who lived more than 600 years ago. This prehistoric approach to metalworking was part of a metallurgical analysis of copper artifacts left behind by the Mississippians of the Cahokia Mounds, who lived in southeastern Illinois from 700 until 1400 A.D. The study was published in the Journal of Archaeological Science in May.

The researchers were able to identify how the coppersmiths of Cahokia likely set up their workshop and the methods and tools used to work copper nuggets into sacred jewelry, headdresses, breastplates and other regalia.

"Metals store clues within their structure that can help explain how they were processed," said David Dunand, the James N. and Margie M. Krebs Professor of materials science and engineering at Northwestern's McCormick School of Engineering and Applied Science and co-author of the paper. "We were lucky enough to analyze small, discarded pieces of copper found on the ground of the excavated 'copper workshop house in Cahokia and determine how the metal was worked by the Cahokians."

Two materials science and engineering students conducted much of the research. Matt Chastain, a Northwestern undergraduate at the time of the study, worked alongside Alix Deymier-Black, a graduate student in the materials science and engineering department. Chastain, first author of the paper, undertook the metallurgical analysis of the samples, supplied from ongoing excavations at Mound 34 in Cahokia. Chastain followed up his analysis by volunteering at the excavation site.

"We cut through some samples of the copper pieces and polished them to look at the grain structures of the copper with a microscope," said Deymier-Black, second author of the paper. "From the size, shape and features of the grains inside the copper, we determined that the coppersmiths were likely hammering the copper, probably with a heavy rock, then putting the copper in the hot coals of a wood fire for five to 10 minutes to soften it and repeating the cycle until they had created a thin sheet of copper. "

After using basic metallurgical science to better understand the methods the Cahokians used to create copper sheets, Deymier-Black and Chastain recreated the metalworking process in the lab with natural copper nuggets, fire and a heavy stone ---pounding and heating the copper into thin sheets.

The researchers also tested theories that some archeologists had made about the coppersmiths' techniques. One idea was that they made large copper pieces, like ceremonial breastplates, by "laminating" sheets of copper together through a hammering technique. Deymier-Black said that the lamination could not be reproduced, even with much greater weights achievable with a modern press. The other hypothesis, that the Cahokians used copper knobs or copper rivets and other mechanical devices to secure sheets of copper together, seems more likely.

Another puzzle was how the Cahokians cut the hammered sheets of copper into regular shapes. The researchers cut replicated hammered sheets by four different methods: grinding an embossed ridge, shearing with scissors, hammering against a sharp corner, and bending the sheet back and forth. Only the bent edge looked similar to the edge of the historical artifacts, indicating that the Cahokians most likely used that method to cut copper.

Scientific insight into the process used to create the sacred copper artifacts of Cahokian people is helpful to James Brown, professor of anthropology at Northwestern Weinberg College of Arts and Sciences and John E. Kelly, professor of anthropology at Washington University in St. Louis. The two researchers, co-authors on the study, are credited with pinpointing the location of the copper workshop at Cahokia.

"I'm delighted that through the scientific process we were able to confirm some of the techniques and end some disputes about how the copper artifacts were made," said Brown, also an international expert on Native American archaeology. "This study gives some of the real details, so that an observer can imagine how it was done and could possibly hook onto other kinds of observations about the people of Cahokia."

Link

footfootfoot · 06-20-2011, 02:51 PM

What's up with all the 10,000 word posts lately?

infinite monkey · 06-20-2011, 03:19 PM

These are subjects which I find fascinating but for which I have no particular opinion, viewpoint, or even any understanding of.

BigV · 06-23-2011, 09:18 AM

I love copper.

It is wonderful to work with and beautiful to look at and handle. Because I have limited resources to anneal the material, or limited experience, my projects have been limited. I have a fountain project that became stalled when the metal was too hard to work. I tried to anneal it but it's a big piece and heheh.. that copper can absorb a LOT of heat. Reading this post makes me think of it and I've a mind to renew my efforts on it. Of course, I have a lot of other projects that are also in need of my attention, so it may still sit idle.

I did complete a project in copper last year and I thought I posted a DIY of the work, but I can't find it.

(The thread that is, the project was completed and given away).

infinite monkey · 06-23-2011, 10:55 AM

I had a job as QA supervisor at a printed circuit board manufacturer, which specialized in multilayers and small aspect ratios and other intricate set-ups. I was in charge of the lab, and we'd cross section boards and test areas built into the boards, after they were copper plated.

It was an amazing process, and an interesting place to work. Very precise specifications.

So I know copper up close and personal. I imagine working with it as art is really neat.

I had an old friend, he was old and died a couple years ago, who made sculptures out of any number of materials. My favorite was a fountain he made and had in his kitchen. Dozens of copper leaves that the water cascaded very slowly down. It was always so comforting.

I wonder what happened to that fountain. I wonder if the new homeowners kept it. It was also the only garage I'd ever seen with a basement. we'd walk around down there with him and he'd say "you like that? Take it." I didn't take much because I didn't want to be greedy. I sort of wish I'd taken more. He was a neat man. Curmudgeon. Funny. Wry. If he didn't like you, you'd know it. He had no filters.

So I can drift my thread all I want, eh?

footfootfoot · 06-23-2011, 11:10 AM

Science: "Uh, yeah. So, it's like really old, and it's made out of, umm, copper. Yeah. That's my story and I'm sticking to it."

infinite monkey · 06-23-2011, 11:20 AM

I love copper. I want to roll around nekkid in copper. You anti-copprite.

I collect malachite, too.

Did you know:

Quote:

Stone-Age people knew nothing of metal. Colorful
minerals were used for decoration or for barter. When
emerald-green malachite (a copper ore) or a rusty-red
hematite iron ore were found, they would be ground
to a powder and used as pigments to decorate the face
and body. They also used these and other colorful
minerals pigments to paint the walls of caves and
protected coves. Today, many minerals are used for
paint pigments.
Can you imagine how excited these people were
when they found native copper? It could be formed
into decorative shapes and tools more easily by
pounding it with a stone on a hard surface. This was
after 6000 B.C. and is known as the Copper Age.

http://www.mii.org/pdfs/copper.pdf

I can imagine. I imagine them standing around pointing at copper saying "well would you just look at that? Just look at it! Look at that!"

There WILL be a test on Friday.

06-20-2011, 01:23 PM	#1
infinite monkey Person who doesn't update the user title Join Date: Mar 2011 Posts: 13,002	Science explains ancient copper artifacts Northwestern University researchers ditched many of their high-tech tools and turned to large stones, fire and some old-fashioned elbow grease to recreate techniques used by Native American coppersmiths who lived more than 600 years ago. This prehistoric approach to metalworking was part of a metallurgical analysis of copper artifacts left behind by the Mississippians of the Cahokia Mounds, who lived in southeastern Illinois from 700 until 1400 A.D. The study was published in the Journal of Archaeological Science in May. The researchers were able to identify how the coppersmiths of Cahokia likely set up their workshop and the methods and tools used to work copper nuggets into sacred jewelry, headdresses, breastplates and other regalia. "Metals store clues within their structure that can help explain how they were processed," said David Dunand, the James N. and Margie M. Krebs Professor of materials science and engineering at Northwestern's McCormick School of Engineering and Applied Science and co-author of the paper. "We were lucky enough to analyze small, discarded pieces of copper found on the ground of the excavated 'copper workshop house in Cahokia and determine how the metal was worked by the Cahokians." Two materials science and engineering students conducted much of the research. Matt Chastain, a Northwestern undergraduate at the time of the study, worked alongside Alix Deymier-Black, a graduate student in the materials science and engineering department. Chastain, first author of the paper, undertook the metallurgical analysis of the samples, supplied from ongoing excavations at Mound 34 in Cahokia. Chastain followed up his analysis by volunteering at the excavation site. "We cut through some samples of the copper pieces and polished them to look at the grain structures of the copper with a microscope," said Deymier-Black, second author of the paper. "From the size, shape and features of the grains inside the copper, we determined that the coppersmiths were likely hammering the copper, probably with a heavy rock, then putting the copper in the hot coals of a wood fire for five to 10 minutes to soften it and repeating the cycle until they had created a thin sheet of copper. " After using basic metallurgical science to better understand the methods the Cahokians used to create copper sheets, Deymier-Black and Chastain recreated the metalworking process in the lab with natural copper nuggets, fire and a heavy stone ---pounding and heating the copper into thin sheets. The researchers also tested theories that some archeologists had made about the coppersmiths' techniques. One idea was that they made large copper pieces, like ceremonial breastplates, by "laminating" sheets of copper together through a hammering technique. Deymier-Black said that the lamination could not be reproduced, even with much greater weights achievable with a modern press. The other hypothesis, that the Cahokians used copper knobs or copper rivets and other mechanical devices to secure sheets of copper together, seems more likely. Another puzzle was how the Cahokians cut the hammered sheets of copper into regular shapes. The researchers cut replicated hammered sheets by four different methods: grinding an embossed ridge, shearing with scissors, hammering against a sharp corner, and bending the sheet back and forth. Only the bent edge looked similar to the edge of the historical artifacts, indicating that the Cahokians most likely used that method to cut copper. Scientific insight into the process used to create the sacred copper artifacts of Cahokian people is helpful to James Brown, professor of anthropology at Northwestern Weinberg College of Arts and Sciences and John E. Kelly, professor of anthropology at Washington University in St. Louis. The two researchers, co-authors on the study, are credited with pinpointing the location of the copper workshop at Cahokia. "I'm delighted that through the scientific process we were able to confirm some of the techniques and end some disputes about how the copper artifacts were made," said Brown, also an international expert on Native American archaeology. "This study gives some of the real details, so that an observer can imagine how it was done and could possibly hook onto other kinds of observations about the people of Cahokia." Link

06-20-2011, 02:51 PM	#2
footfootfoot To shreds, you say? Join Date: Aug 2004 Location: in the house and on the street-how many, many feet we meet! Posts: 18,449	What's up with all the 10,000 word posts lately? __________________ The internet is a hateful stew of vomit you can never take completely seriously. - Her Fobs

06-20-2011, 03:19 PM	#3
infinite monkey Person who doesn't update the user title Join Date: Mar 2011 Posts: 13,002	These are subjects which I find fascinating but for which I have no particular opinion, viewpoint, or even any understanding of. Last edited by infinite monkey; 06-20-2011 at 03:27 PM.

06-23-2011, 09:18 AM	#4
BigV Goon Squad Leader Join Date: Nov 2004 Location: Seattle Posts: 27,063	I love copper. It is wonderful to work with and beautiful to look at and handle. Because I have limited resources to anneal the material, or limited experience, my projects have been limited. I have a fountain project that became stalled when the metal was too hard to work. I tried to anneal it but it's a big piece and heheh.. that copper can absorb a LOT of heat. Reading this post makes me think of it and I've a mind to renew my efforts on it. Of course, I have a lot of other projects that are also in need of my attention, so it may still sit idle. I did complete a project in copper last year and I thought I posted a DIY of the work, but I can't find it. (The thread that is, the project was completed and given away). __________________ Be Just and Fear Not.

06-23-2011, 11:10 AM	#6
footfootfoot To shreds, you say? Join Date: Aug 2004 Location: in the house and on the street-how many, many feet we meet! Posts: 18,449	Science: "Uh, yeah. So, it's like really old, and it's made out of, umm, copper. Yeah. That's my story and I'm sticking to it." __________________ The internet is a hateful stew of vomit you can never take completely seriously. - Her Fobs

06-23-2011, 10:55 AM	#5
infinite monkey Person who doesn't update the user title Join Date: Mar 2011 Posts: 13,002	I had a job as QA supervisor at a printed circuit board manufacturer, which specialized in multilayers and small aspect ratios and other intricate set-ups. I was in charge of the lab, and we'd cross section boards and test areas built into the boards, after they were copper plated. It was an amazing process, and an interesting place to work. Very precise specifications. So I know copper up close and personal. I imagine working with it as art is really neat. I had an old friend, he was old and died a couple years ago, who made sculptures out of any number of materials. My favorite was a fountain he made and had in his kitchen. Dozens of copper leaves that the water cascaded very slowly down. It was always so comforting. I wonder what happened to that fountain. I wonder if the new homeowners kept it. It was also the only garage I'd ever seen with a basement. we'd walk around down there with him and he'd say "you like that? Take it." I didn't take much because I didn't want to be greedy. I sort of wish I'd taken more. He was a neat man. Curmudgeon. Funny. Wry. If he didn't like you, you'd know it. He had no filters. So I can drift my thread all I want, eh?

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