History Forum / General / Archaeology / April 2007

On Apr 28, 12:14 pm, Jack Linthicum <jacklinthi...@earthlink.net>
wrote:

add: http://links.jstor.org/sici?sici=0093-4690%28199624%2923%3A4%3C477%3AABDCOC%3E2.
0.CO%3B2-X&size=LARGE&origin=JSTOR-enlargePage

Journal of Field Archaeology

This journal is licensed to JSTOR by
Boston University
Arsenic Bronze: Dirty Copper or Chosen Alloy? A View from the Americas
Heather Lechtman
Journal of Field Archaeology, Vol. 23, No. 4 (Winter, 1996), pp.
477-514
doi:10.2307/530550
This article consists of 38 page(s).

First page of requested article: Arsenic Bronze: Dirty Copper or
Chosen Alloy? A View from the Americas

Abstract

Archaeologists and historians of metallurgy have attempted to explain
the gradual abandonment of arsenic bronze in favor of tin bronze in
the ancient Old World by making comparisons between the mechanical
properties of the two bronzes. These comparisons purport to show the
superiority of copper-tin alloys over alloys of copper and arsenic,
despite an absence of data on the physical properties of the copper-
arsenic system. The study reported here presents the results of
mechanical tests carried out on experimental samples of both types of
bronze over a broad range of alloy compositions. Hardness, tensile
strength, and elongation determinations were made on cold worked and
hot worked (forged) material. Whereas tin bronzes can be work hardened
more extensively than arsenic bronzes, the far greater ductility of
arsenic bronze makes it a desirable alloy for the manufacture of thin
metal sheet. The widespread use of low-arsenic copper-arsenic alloys
in the Americas, especially in the Andean culture area, is
attributable in part to the tradition there of sheet metal production
in the elaboration of three-dimensional forms.

and
Almost all copper ores contain some small proportion of arsenic, tin,
zinc, antimony, or nickel, which mixes at the molecular level with the
copper during smelting‹in other words, a tremendous number of subtly
different alloys can emerge out of a smelter after a mixture of ore
has been smelted, even though the geologist has been skilled enough to
select ores that are rich in copper. The alloys are still dominated by
copper, but the alloy has a lower melting point than pure copper,
which allows easier melting and casting. The castings are better
quality, and the alloy is much harder than pure copper after it has
been worked by hammering. Paradoxically, the less pure copper ore that
was available, the greater the variety of alloy the smith would
produce from his smelter. By trial and error, early metallurgists
(smiths) would soon come to associate a particular mixture of ores in
the furnace with a particular result. In time, a skilled smith would
be able to have some control over the end product, producing not
copper, not a random unknown alloy, but a specific alloy to suit the
job at hand. The Bronze Age marks the time at which smiths became
metallurgists, makers of magic, heroes, and gods. Bronze Age smiths
were often buried with the tools of their trade: hammers, an anvil,
knives and molds.

Bronze is any alloy that is 85-95% copper, with the other 5-15% made
up of mainly of tin or arsenic, though other metals can be present in
small amounts. http://www-geology.ucdavis.edu/~cowen/~GEL115/115CH4.html

No, it is Inger E. Johansson , which usually
does not mean 'misleading', but 'plainly wrong'.

Digger <p.dunn1@hotmail.co.uk> skrev i
diskussionsgruppsmeddelandet:W%lYh.1174$N05.334@newsfe3-gui.ntli.net...

Only for fools who can't read the lines I wrote! Are you such?

Inger E

She also changed the focus from North to South America
and from Late Archaic and Early Woodland to Inca.

Alan Crozier <name1.name2@telia.com> skrev i
diskussionsgruppsmeddelandet:MKFYh.39591$E02.15900@newsb.telia.net...

No I don't. But you seem to have missed the last sentences in my first
article to the group.
"....this seem to indicate either that people with knowledge of what to look
for
and how to 'process'/use the Copper at least might have made same 'finding'
as done in parts of the Old World where Bronze first were found/made from
Copper melting in charcoal fires. Provided of course that at least some
tinoxide existed in Copper raw material as it did here in the Old World."

What I learnt over the years as a teacher from schoolbooks as well as when I
studied this parts at university is the same as told at this url
<http://susning.nu/Brons> ".....Av en ren slump upptäckte man att vissa
kopparmalmer, som även innehöll tennoxid, kunde rödglödgas i träkolseld, så
att legeringen brons bildades." I don't hesitate to think that same finding
of the alloy could have been made anywhere in the world where the Copper ore
contained Tinoxide.

All. Look at what the Inca's made before the Spaniards arrived. Gold items
which had decorative stones and allows which in some cases Goldsmiths today
have hard when trying to copy. Bronze tools and weapons, as I wrote in a
previous answer.

That's not what I was saying. Please read the Swedish text again and than
the quote from my first article under this subject line. It's crystal clear
what I mean if you do and that's why I suggested that you looked up 'Brons'
Swedish spelling in Google.

Neither of the possibilities you suggested is valid in the Bolivian Bronze
cast case, 1100 AD.
There are two possible cases and only three.
*Either Bronze was known at least somewhere in South America prior to 1100
AD.
or
* By coincidence archaeologists managed to find the case where Bronze first
came to be produced in South America.

Now both possible answers in themselves give two possible ways for the
knowledge of how Bronze came to be produced in Bolivia:
* Either the first 'production' in the New World came to be due to pure
coincidence during melting of Copper ore which had tinoxide in the ore.
(Note that this could and probably did happen in many places over so many
thousand years when Copper was melted).
or
* The first 'production' was a result of Diffusion, one way or an other.

No other possibilities exist. Chose which one you like, but I would think
the first possible answer in each of the two lines to be at least more
probable than the second answers.... At least from what we know today.

Inger E