Choosing Which Metal To Use: Part 3

Last week we asked if there were any other issues with metal that we should consider. Well, two things come to mind immediately: metals other than bronze and lead, and knowing your metal source.

Metals were not carefully assayed in the past they way they can be today. The people who created the various pure metals and alloys were knowledgeable, and there is a considerable amount of pre-1600 written material about creating various alloys, but metal purity could not be tested with the same level of precision that we have modernly. Many alchemy texts have information on metallurgy.

When you are reading museum data base entries, the actual metal content of a piece is rarely listed. “Copper alloy” is often used to refer to any sort of bronze metal and the actually purity of precious metals is rarely noted. Until recently it has been much too expensive to test each piece to determine exactly the metal content. Larger organizations, like the British Museum, will sometimes reevaluate pieces as they clean them, and they sometimes test the metal content. Testing content has helped to reveal frauds, and modifications of artifacts, many of which were done in antiquity.

For anyone who has ever followed the types of silver that are available modernly, the two most common would be Sterling Silver (also designated as .925) and Fine Silver (.999).  Those numbers simply indicate the percentage of silver that is included in the alloy. There are other designations, including coin silver (which varies in silver content depending on the date of manufacture and the country), and Argentium Silver (which is a tarnish resistant form of Sterling Silver with special properties). The terms Bali Silver, Thai Silver, and Mexican Silver may be used in a retail setting, but have no legal meanings. Nickel Silver, or German Silver is silver colored, and does not actually contain any silver at all. It is a copper alloy.

There were an assortment of silver alloys that were used in period that are not usually used modernly. Billon has been used since at least ancient Greece. It is a silver colored alloy which usually contains silver and other metals (usually copper), and may sometimes contain mercury. It was commonly used for making coins and medals. Electrum is a naturally occurring alloy of silver and gold, which has been used since at least 3,000BC by the ancient Egyptians. It was used widely in coinage and jewelry manufacture by cultures as varied as the Egyptians and the Vikings. There are major deposits of natural electrum in Anatolia (Turkey).

All of the silver pieces that I currently make for sale in my shop is classified as Sterling Silver. My cast pieces are solid sterling, and the wire and plate that I use in my toiletry sets, needles cases and chains (both knit and link) are all solid Sterling Silver.  I do not currently work with Argentium silver. Sterling Silver alloy was used during Medieval times.

Next time: What about silver plate, silver filled, vermeil, and gold filled metals, and sources of metal?

Choosing Which Metal To Use

I often hear conflicting complaints from historic re-enactors and SCA folks alike:  “the problem with my group is too many authenticity Nazis” and “why can’t people at least make a more accurate attempt at their clothes?”

As a professional jeweler and merchant at SCA events, I frequently wrestle with the disparity of these sentiments. Some of the choices are difficult, but some are easy from my perspective. I make many of my items using a copper alloy known as bronze. Some merchants choose any old copper alloy without regard to what would have been used historically. But using true bronze gives my pieces the look and feel of the originals that they are patterned after.

Bronze was used to make weapons, armor, knives, brooches, hooks, crosses, and many, many, other items. It’s a ubiquitous material throughout Medieval history, and much earlier. Bronze is a remarkable alloy with multiple formulations. The first bronze included copper and arsenic (yes arsenic). Fortunately for real sticklers for accuracy, arsenic bronze was largely replaced by a tin and copper formulation that we recognize today as true bronze. A bit of good news for authenticity fans – true bronze became the primary bronze from the 3rd millennium BC.

There are very few places on the earth where copper and tin are found together (one site each in Thailand and Iran), so true bronze is reliant on trade. Great Britain was the major source of tin in Europe, which can explain some of the unusual trade goods found in Britain.

Copper alloys are truly remarkable. They can be harder than wrought iron, be sharpened for cutting edges, and the alloying process is comparatively easy. Depending on the alloy (tin, zinc, lead, silver and other additives) the metal can take on many different hues. Each formulation has unique characteristics, and in our modern society they have very specific names – brass, yellow brass, and nickel silver, to name a few. Some alloys are malleable, others are hard and brittle, and still others have differing degrees of chemical resistance.

Are there any other practical reasons for me to want to use true bronze instead of some other bronze alloy? Yes. True bronze can be enameled. Now some of the other alloys can be enameled, too. But the problems with enamels changing color because of the zinc in brass, for example, can be difficult to overcome. True enamel is a form of ground glass that is melted and fused to the metal. If you are interested in more detail about enamel and enameling, just visit my enamel blog.

Handled ewer. Copper alloy with champlevé enam...

Handled ewer. Copper alloy with champlevé enamel, Late Roman work. (Photo credit: Wikipedia)
















Today we know that iron replaced bronze for knives, weapons, and many other larger items, as iron working skills matured. Iron could maintain a sharp edge longer, withstand greater bending forces, and eventually could be made into steel. The transition to iron seems to have been encouraged along by a tin shortage. Around 1200 BC the shipment of tin around the Mediterranean plummeted – coincident with population migration. There’s no definitive proof of the link between migration and the tin shortage, but some archaeologists believe that there is a causal relationship between the two.

But are there any other metal choices that we need to make for period reproductions? We’ll talk about that next time.