Regarding Dave Baldwin's question on the definition of bronze, Jack Howes writes:
The terms brass and bronze have become so muddied that they don't mean much if anything
specific anymore. I would call all those medals copper with trace amounts of alloy with the one
exception that was 2% zinc which is a true copper-alloy.
Gosia Fort writes:
The same question was nagging me when I was researching medals from my collection. In one
catalog a medal can be described as copper, in the other - as bronze. What proof does the author
have to choose one name over the other if he did not test the alloy? (I do not think that either
Freeman or Storer examined the chemical content of each medal when they were compiling their great
works). So I came to a very simple conclusion - that numismatists use the metal name in a common
sense; they describe more the look of it than the content. For a chemist it may matter that the
brass is an alloy of copper and zinc, while bronze is a mix of copper and tin, but for a
numismatist (especially a newbie like myself) it may be OK to go with a common sense and a duck
test for those few medals I could not find authoritative reference. I will call a copper anything
that looks like a copper, a bronze - any shades of brown, a brass – anything with hues of yellow.
After all, I am looking at the medals and describing them as objects of art.
Paul Schultz submitted a response on this topic back on March 18, 2012. Here it
I read the brass & bronze definitions in last week’s E-Sylum, and thought I might
clarify it from a metallurgist’s point of view.
The problem comes about in the origin of the names, from tradition dating back hundreds of years
for some specific alloys, vs. modern definitions for general groups. The modern metallurgical
definitions I was taught in my courses for a Master's degree in metallurgy reveal a confusing
difference between alloy groups and specific alloys.
For the general categories, the definition of a brass is copper alloyed with less than 40% zinc,
and no other elements. Copper with over 40% zinc is Muntz metal. Copper alloyed with anything other
than zinc, (especially tin, but also aluminum, nickel, etc, and it may also include zinc along with
these other elements) is considered a bronze alloy. An aluminum bronze is copper with aluminum plus
possibly other elements, nickel bronze is copper with nickel plus possibly other elements, etc.
The confusing problem is the overlapping traditional naming for the very specific alloys, which
go back hundreds of years, and which are not fully consistent with the above modern system.
“Commercial Bronze”, composed of 90 copper and 10 zinc, is really a brass alloy by modern
definition. “Aluminum brass”, at 76 copper, 22 zinc, and 2 aluminum, is really in the bronze
The situation creates more confusion than it alleviates. Specifically for coinage, I believe
that most of the copper zinc alloys that are used have a more golden color, and the copper tin
alloys have a lighter color. For coinage, it may be more practical to use the modern category
definitions which are more consistent with the colors we see in coinage, and ignore the specific
traditional names like “Commercial Bronze”. Reference for most of the above is “Physical
Metallurgy for Engineers”, Donald S Clark and Wilbur R Varney, Van Nostrand 1962, pp
Paul was responding to a note by Dick Johnson. As it turns out, Dick was very much
in agreement with Gosia's assessment.. -Editor
So what is the difference between bronze and brass? If the zinc is less than 10% it is bronze.
But numismatists are not satisfied with the term at this precise formulation.
For numismatists -- who can best describe an item by inspection -- the term is determined by
color. If the piece is brown it is bronze. If it is golden yellow it is brass. But the color of the
metal alloy doesn't change until the zinc content is above 15%, or as expressed in the
metalworking trades, copper 850 zinc 150. This adds to 1000, but sometimes expressed .850 and .150
to add to 1 -- the total amount.
Technically that area between 10% zinc and 15% zinc alloyed with 90% to 85% copper is called red
brass. At zinc 160 copper 840, one percent more zinc you find a solid yellow-brass color. This
continues as the amount of zinc increases. However red brass is not permanent. Like a freshly
struck U.S. cent it is copper-red color that after about six month's time harsh exposure or
much handling in circulation has turned brown. It is the copper content that causes the color
We could not have all the world's coins if we did not have copper. The alloys of copper for
numismatic items have been called many things. But it's okay to call brown coins or medals
"bronze" and golden yellow coins and medals "brass."
Dick Johnson submitted these additional thoughts for today's issue. Thanks!
WHAT IS BRONZE? WHAT IS BRASS?
When I went to work at Medallic Art Company I was charged with writing about the company and the
products. I quickly realized I needed to learn the lingo, the language of the medallic field. I
started writing down the words, the terms everyone was using that I didn't know for sure.
The first two were cartouche and cliché. I would ask what each word meant. The workmen, foreman,
and management were all kind, they took the time to answer all my questions.
Bronze was one of those words that was widely used -- didn't everyone already know? -- but
late to be defined. Years later I studied the use of the term "bronze" in all of its uses
not only in numismatics, but also in metalworking, It is so closely associated with brass I had to
study that as well.
What ended up was a chart of 24 kinds of bronze-brass terms. Coins were made in a select few of
these, medals were made in just about every one. But they all fit in that one chart.
For a three-year period I wrote a Monday Report for the new management of the company. I wrote
one of those Reports on bronze-brass and included that chart. Management liked it so well they
placed in on the firm's web site available for all.
In numismatics we most often describe an item by its color. Bronze will tone brown, brass is a
golden color. Both are a copper alloy. What I learned that the alloy changes color because of a
second metal copper is alloyed with.
When copper is alloyed with zinc if the zinc content is more than 16% the metal is a golden
color -- brass. When it is alloyed with 15% or less zinc it will become a brown color -- what
everyone calls bronze. The alloy changes color between 15 and 16 percent zinc.
Of course, when copper or bronze is freshly struck it is red. It tones brown in short time; the
brown color is permanent. Brass will tone but still retains its golden color. This may not be the
last word on the subject, but you can read that report online [Link below - Editor]
To answer Dave's question about "bronzed copper" or "chocolate bronze"
these are terms of its patina. These are not terms of the composition. However, patinas are a
subject for another article.
To read Dick Johnson's Medal Blog article, see:
Is It Bronze Or Is
It Brass? (medalblog.wordpress.com/2012/03/12/is-it-bronze-or-is-it-brass/)
Dave Baldwin adds:
Anyone who wishes to continue the conversation can contact me at email@example.com . And John Kraljevich said
bronze was "any non-red copper alloy". That's pretty simple!
To read the earlier E-Sylum articles, see:
NUMISMATIC VOCABULARY: BRONZE VS BRASS
ON BRASS, BRONZE, AND GOLDENE
QUERY: WHAT IS THE DEFINITION OF
Wayne Homren, Editor
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