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V15 2012 INDEX       E-SYLUM ARCHIVE

The E-Sylum: Volume 15, Number 12, March 18, 2012, Article 18

ON BRASS, BRONZE, AND GOLDENE

Last week I published a submission from Dick Johnson containing this paragraph:

All of these copper alloys have been used for coins under a variety of terms for the various compositions. These include French bronze, tombac, Dutch metal, Mannheim gold, copper-nickel, and ultimately oroide or goldmine. The latter is at 33% zinc content with an obvious brass-gold color.

Dick writes:

My spellchecker did this to my text -- Sorry! The correct word should have been goldene -- which can also be spelled goldine. (Osborne Coinage spelled it this way, they struck a lot of tokens and medals in this composition.) It is a brass composition often confused for bronze gilt, but there is no gold in goldene.

I missed this too. Sorry! We'll fix our archive. -Editor

Bob Neale writes:

I don't wish to be argumentative, but I would like to note this in regard to the learned Dick Johnson's write-up about the composition of brass vs bronze. Most people, especially chemists, consider bronze to be a mixture of copper with tin (and sometimes other things), but not with zinc. Brass is copper with zinc (and in my recollection, often some tin as well). My point is that DJ's comment that "If the zinc is less than 10% it (the copper alloy) is bronze." may be misleading, as this implies that bronze can contain a significant percentage of zinc. (But maybe it can among coinage metallurgists.)

Paul Schultz writes:

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 series.

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 392-393.

To read the earlier E-Sylum article, see: NUMISMATIC VOCABULARY: BRONZE VS BRASS (www.coinbooks.org/esylum_v15n11a10.html)

Wayne Homren, Editor

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