The metals of antiquity – tin

The first known examples and uses of tin are in bronze, which we started producing in the Middle East around the late 4th / early 3rd millennia BC. Some authorities² have suggested that initially we probably didn’t realise we were dealing with a different ore, one that contained copper and various other minerals, and that we chanced upon the production of copper alloys through natural contamination of the copper ores we were smelting.

“Purification of smelted copper was not practised until the sixteenth to seventeenth century AD; therefore, in the Bronze Age the purity of the extracted metal depended entirely on the type of available ores.”³

As the earliest bronze objects found to date contain minute quantities of arsenic and/or tin (around 2% or less), this suggests that the alloys were indeed the result of chance rather than intent.

Incidentally, even these miniscule amounts were enough to make noticeable changes to the properties of the copper that was being produced.⁴

Archaeologists have also discovered that arsenical bronze predates tin bronze because they’ve found traces of arsenic rather than tin in the very earliest Bronze Age tools. These tools come from the transitional era between the Neolithic Stone Age and the Bronze Age ‘proper’, an era often referred to as the Copper or Chalcolithic Age. The Copper Age is generally accepted to have run from around 4,500 BC to 3,000 BC or even 2,500 BC in some regions, and during this time arsenical copper was widely produced and used in tools and various other implements.

For instance….

We introduced you to ‘Frozen Fritz’ AKA Oetzi the 5,300-year-old Iceman in our article on copper and mentioned that his hair tested positive for high levels of arsenic (and copper). This provides a clue that he probably worked in, or lived close to, a copper smelter that was processing copper/arsenic ores. The smelter was likely producing a typical arsenical bronze for the time ie copper with minute quantities of arsenic present.

He was also found with an ‘almost’ pure (99.1%) copper axe head but in this instance the impurities, namely arsenic (0.2 wt-%), silver (0.1 wt-%), oxygen (~.5 wt-%) and ‘other’ (<0.1 wt-%), have been attributed to the wood used to fire the smelters. Interestingly, these were able to tell researchers ​ that the copper in the axe head came from the Tuscany region in Central Italy, and not from copper deposits closer to where he was found.

From around 3,000 BC there was an overlap between the production of arsenical bronze and the gradual development of tin bronze. Certainly circa 3,000 BC is typically associated with the beginnings of tin use, and the primary use of tin so far discovered this far back in history was as an alloy in bronze. A few pieces of tin jewellery ie beads and similar trinkets, have been found but they’re very rare and not considered historically significant in relation to prehistoric tin use.

Arsenical bronze production subsequently died out but whether this was because tin bronze met the needs of the time better, or metal workers had realised by now that arsenical bronze was causing health issues, has never really been established.

General consensus amongst archaeologists is that the former is the most likely explanation. Arsenical bronze did make a comeback much later because, amongst other things, it can be hammered into thin sheets that were ideal for steam engine casings and the like.

Design Or Accident?

Unfortunately, although they were producing tin bronze in ever increasing amounts, history doesn’t pinpoint exactly when metal workers figured out they were dealing with different metals in their copper ore, and started sourcing those metals directly in order to control the quality of the alloys being produced. What we do know is that it seems to have happened at different times in different parts of the world as word of the ‘new technology’ spread along trading routes.

Southern European and Middle Eastern bronze production

The earliest tin bronze artefacts, dating to around 3,000 BC, have been found in the Middle East and around the Mediterranean, indicating that this was likely where it started. Until recently though the source of the tin used during these early Middle Bronze Age centuries was a mystery. None of the currently known prehistoric tin workings were old enough to have provided the tin for this bronze.

An Ancient Mystery Solved At Last!

The discovery of ancient tin workings in Southern Turkey ​late last century provided the first solid clues to the millennia old mystery of just where the tin used in the earliest tin bronze artefacts came from! The vast expanse of underground workings appear to have been mined for around 1,000 years from 2,870 BC to about 1,870 BC, whilst the open cut workings above them are somewhat older and dovetail nicely with the development of tin bronze in this region.

In contrast, ancient tin mines in Europe are very rare. This is probably because the prevailing weathering conditions in Europe favoured the development and mining of alluvial tin deposits. Unfortunately, the topography and equipment used to work these deposits have not stood the test of time like those in the open cut and underground workings across the more arid regions of the Middle East. Therefore, many of them have disappeared into the mists of time, making it almost impossible to accurately identify the tin that may have come from them.

That’s why finds like the tin ingots from a couple of Bronze Age shipwrecks (Uluburun near Turkey and Salcombe off the south coast of England) and dating to the mid to late second millennium, are so significant.

They add rare and valuable clues about the history of Bronze Age tin use in Europe. In this case, the ingots were almost certainly destined for use in bronze smelters in Europe and perhaps further afield, thus providing strong evidence about the existence of tin trading in and around Europe and the Mediterranean during the latter part of the Middle Bronze Age era. It also tells us that the practice of controlling bronze production by the addition of specific quantities of tin was by now widespread.

Further evidence of tin trading is also found in the specific references to tin that begin to appear in the writings of Phoenician traders around 1,500 BC. Phoenician colonies in southern Spain had been actively involved in commodities trading with other colonies for some time by the middle of the 2nd millennium BC. There were comprehensive trading networks across Europe, the Middle East and into Asia and clearly tin was being transported along these routes as well. As time went on, centres like Cadiz (Gadir), a colony founded between 800 and 600 BC close to the Guadalquivir River, were set up to trade locally produced tin and silver.

Across the Channel, England’s ancient and famous Devon and Cornwall tin workings were first mined around 1,800 BC, although some sources put it earlier at around 2,150 BC (historical discrepancy at work!). Tin from these mines subsequently made its way around the Mediterranean and across much of Europe, and brought the south of England in particular into the existing trade networks of the time.

For many years it was presumed that most of the tin used in European bronze came from the Erzgebirge Mountains on the Czech / German border. However, scientific studies⁶ on the Nebra sky disk and a pure tin ingot in Scandinavia ​have found that the tin in these objects comes from Cornwall. Current thinking therefore, based on admittedly limited evidence, is that the early tin used throughout Northern and Central Europe originated in Cornwall. Interesting sidenote – England’s tin and established mineral wealth in general were a large part of the reason the country found itself a target for Roman takeovers! It also didn’t help that its citizens had a habit of supporting the Gauls in their tussles with the Romans….

In Asia, ancient tin mines have been discovered in East Kazakhstan ​(~2nd millennium BC) and West Central Iran​ near Deh Hosein. The latter is a huge copper / tin / gold deposit whose workings have also been dated to the mid 2nd millennium BC.

Moving further east, there is a big tin belt running from Yunnan in southern China to the Malay Peninsula with ancient workings that supplied the tin for Chinese bronze from around 1,700 BC to the modern era. Prior to that, most of China’s tin is believed to have come from the Yellow River, which some sources say was mined from 2,500 to 1,800 BC although by who is unclear. The workings have been variously attributed to the Erlitou ​(~1,900 to 1,500 BC) and the Shang Dynasty (~1,600-1,046 BC) but the dates are somewhat problematic! This is actually typical of so much of the early documented history of tin. We’re talking about a period of time that predates the written word in most parts of the world so are relying on modern dating technology, which is often not as reliable as one might think and in some cases can only provide a range of dates.

“Relative dating has its limits. Its techniques are often subjective, and an artefact’s location within a site or relative to other objects may not reflect its actual chronological age, as things may have gotten shifted around at some point in time. For a more precise date, archaeologists turn to a growing arsenal of absolute dating techniques.

Absolute dating has its drawbacks: Techniques can be expensive and provide less clarity than their name might suggest. Radiocarbon dating, for example, can only be performed on objects younger than 62,000 years old, only results in date ranges, and can be thrown off when objects come into contact with younger organic material. Nonetheless, newer dating techniques have expanded archaeologists’ ability to home in on sites’ ages and histories.”⁷

China’s Bronze Age is generally accepted to have started somewhere between 2,000 and 1,700 BC, depending on the source of the information, and roughly parallels that of Central and Northern Europe. There’s also some speculation that many of the renowned early Chinese bronzes may in fact have originated in Africa, or at least some of the components in them did⁸. If this is true, it somewhat flies in the face of the theory that the Far East didn’t have much trade contact with the rest of the world at that time!

Uses For Tin​

The Bronze Age eventually started to peter out around 1,200 BC as iron became the new ‘norm’. Tin however continued to play a significant role in the development of human civilisations, as did bronze incidentally. Iron, it was found, was great for some things but not so great for others. Bronze made better weapons for instance and so bronze, and therefore tin, continued to be the metal of choice for these items until steel, somewhat inadvertently, came along.

Apart from their dominance of the ancient tin trade, the Phoenicians were also famous for their purple dye. Tin vessels were ideal for storing the dye whilst the liquids evaporated, so it’s probably fortunate they could conveniently lay their hands on it fairly easily.

The Romans ‘welded’ together some 400 kilometres of lead water piping using an alloy made from tin and lead. Today, tin remains an important component in modern solders thanks to its strength and wetting ability. Over 50% of today’s tin is used to make the various types of solder that come in handy for everything from plumbing through to electronics, cars and machinery.

The other object most commonly associated with tin is the humble object that gets its name from the metal, or at least from the fact that until the middle of last century they were made from thin rolled plates of steel coated in tin, called tinplate steel. The edges of the rolls were then soldered together with tin-lead solder. The steel provided the strength whilst the tin prevented rust. Today, most tin cans are made of aluminium but there are still enough of the old school ones being produced to use some 20% of the tin produced. The tin lead solder though is out, replaced by safer tin alloy solders.

Tin electro-plating is somewhat similar; the thin coating of tin around metals that are prone to corrosion protects them and allows the product to be made into a range of items including kitchen utensils, stationery items (paper clips, pins), circuitry, and the like.

Tin bronze is still used today to make a range of products from statues to car engine and machinery bearings, and musical instruments (mostly percussion ones) – bell metal in particular uses a lot more tin than regular bronze in order to produce the special resonance that bells produce. It’s also used in electrical equipment and in heating, ventilation, air conditioning and other similar products, washers and springs, medals, nautical equipment and more.

The glazes seen on various types pottery (tiles, vessels etc), and glassware are tin oxide, which may be left white (its natural colour) or coloured with other types of metal oxides. Plate glass gets its lovely flat, polished surface courtesy of floating on a lovely flat, polished surface of molten tin whilst it solidifies and hardens. Spraying glass with tin salts produces electrically conductive coatings whilst other tin salts have a wide range of uses as reducing agents, in biocides, for making dyes, as colour fixing mordants, in toothpaste, as stabilisers, fire retardants and so on.

Most of us have at least one pewter object in our homes! Pewter is of course made from tin (~91%), antimony (~7.5%) and copper (~1.5%). Once upon a time it also contained lead. Tinsel is also made from very thin sheets of tin.
Tin has many desirable qualities. It isn’t magnetic, it’s highly corrosion resistant, durable, soft, malleable, ductile, lightweight, and non-combustible. That makes this silvery-white metal a very valuable commodity with a wide range of uses. 

(This article first appeared in Mining International Ltd.)

Bibliography:

[1] https://en.wikipedia.org/wiki/Metals_of_antiquity

[2] Penhallurick, R.D. (1986), Tin in Antiquity: its Mining and Trade Throughout the Ancient World with Particular Reference to Cornwall, London: The Institute of Metals, ISBN 0-904357-81-3

[3] https://www.cambridge.org/core/journals/antiquity/article/representations-of-oxhide-ingots-in-scandinavian-rock-art-the-sketchbook-of-a-bronze-age-traveller/A09F2EEC28FAAEB166CABC172D12FB6D

[4] https://www.researchgate.net/publication/326312521_Archaeological_Arsenical_Bronzes_and_Equilibrium_in_the_As-Cu_System

[5] https://eurogeologists.eu/powell-unearthing-europes-bronze-age-mining-heritage-with-tin-isotopes-a-case-study-from-central-europe/

[6] Haustein, M.; Gillis, C.; Pernicka, E. (2010), “Tin isotopy: a new method for solving old questions”, Archaeometry, 52 (5), pp. 816-832, doi:10.1111/j.1475-4754.2010.00515.x

[7] https://www.nationalgeographic.com/culture/article/archaeologist-methods-date-sites-artifacts

[8] Origin of the mysterious Yin-Shang bronzes in China indicated by lead isotopes; Wei-dong Sun, Li-peng Zhang, Jia Guo, Cong-ying Li, Yu-hang Jiang, Robert E. Zartman & Zhao-feng Zhang https://www.nature.com/articles/srep23304