What have the Romans ever done for us? How about gold from stone!

Cactus plant in brass pot.

Cactus plant in brass pot. Photo by Stephanie Harvey on Unsplash.

As the scene from Monty Python’s Life of Brian goes, the Romans have given us the aqueduct, sanitation, roads, irrigation, medicine and, of course, the wine. But is that all? Far from it, as they also gave us a new alloy by combining copper with zinc. They were the first to master a specialised technique for mixing the two metals to make brass in a standardised way. Once introduced in large scale, brass had a lasting impact throughout and following the Roman Empire, and it is still widely used today.

Brass is unlike most alloys used in antiquity, because zinc will evaporate at temperatures when copper would still be in stolid state. This means that the two metals cannot not be combined in liquid state such as with the much more straightforward case of bronze (a mixture of copper and tin). Nevertheless, some early brasses were known already from prehistory. These pre-Roman brasses are best described as natural alloys resulting from the smelting of zinc-rich copper minerals in reducing conditions (lack of fresh oxygen). However, these early brasses had variable and lower zinc contents and were available in much smaller scale compared to their Roman counterparts due to the lack of a standardised method.

The Romans solved this metallurgical riddle that was not possible to tackle for most of the Iron Age. They understood and perfected a technique for mixing copper and zinc, namely cementation. During this process, copper metal, zinc minerals and charcoal were heated in high temperatures in airtight vessels, namely lidded crucibles. At around 900-1000 ℃ and with some help from the charcoal, the zinc oxide charge was transformed to zinc metal as gas, which was then diffused in the copper. The result was brass, an alloy with improved strength, corrosion resistance, and formability, and similar looks to gold. But crucially, it was cheaper than gold.

With the product of every new technology, comes a new way of expressing ourselves. High-zinc, standardised brass was important not only for its enhanced material properties and economic attributes – as it is significantly cheaper than bronze too, but also for its appearance. To the untrained eye and without a direct comparison, a brass object will seem gold. This is the reason why much of the post-Roman metal jewellery and ornamental pieces are made with brass. The Vikings did it, the Persians did it, and we do it today.

Brass door

Brass door with islamic decoration. Photo by Nicolai Plenk on Unsplash

Metals are not just functional items. Their aesthetic properties convey important information about their makers’ and users’ belief systems and identity. Brass with its golden colour, yet cheaper and more durable than gold, provided new avenues for identity expression. Think of people who routinely choose between silver or gold jewellery, as they identify with one colour but not the other. One significant contribution of brass was that one need not be able to afford gold to own and wear jewellery that appeared golden. There are several examples of past cultural groups, which consciously used the colour of metal for self-identification. Silver and gold, for instance, were associated with the moon and the sun and further with female and male identities in Meso- and South American cultures.[1] Similarly, in early 1st mil. AD eastern Mediterranean, pagan (Roman) communities were more likely to use brass to distinguish themselves from Jewish groups, which preferred bronze.[2]

The importance of brass though extends beyond its looks or its value. The mere fact that from a mineral which resembled a stone one could make a metal which looked like the noblest of all, namely gold, fascinated early metallurgists. The quest for making gold from stone gave rise to a branch of alchemy called chrysopoeia, literally meaning gold-making. The experimentation of alchemists in medieval times with these processes formed the basis for what we know today as the science of chemistry.

Even though not many today would look to make gold from stone, brass continues to be made and will be made in the future for its functionality, looks and low value. It all started with the Roman’s flare for large-scale production across an extensive exchange network, but brass continues to be all around us. We use brass in our homes and industry, for expressing our sense of aesthetics with jewellery and ornaments, and for immersing ourselves in the melodies of musical instruments.

 

Sources

[1] Mendoza, R.G. 2008. “Metallurgy in Meso and North America.” In Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures, edited by Helaine Selin, 1636–1639.

[2] Ponting, M.J. 2002. “Keeping up with the Romans? Romanisation and Copper Alloys in First Revolt Palestine.” IAMS 22: 3–6.

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Vana Orfanou

Postdoctoral archaeological scientist working with past technologies at UCD, Dublin. Analysing all things metallurgy and talking about past peoples' ideologies.
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