Workshop Basics: Which metals?

by Jamie Hall on February 19, 2010

Before I can choose a furnace design (or several) I need to know what kind of fuel I will be working with. The obvious choice seems to be charcoal, but I’ve considered various others. Before I can choose a fuel, I need to know what temperatures I’m expecting from it.

According to Cookson, the top melting point for stirling silver is 890C, while fine silver is a bit higher. In the immediate future I will be working with stirling, even if it is not a historical alloy, because I have access to plenty of scrap metal at cheap prices. Because I work in the modern jewellery trade, I may be able to purchase old silver items from customers who bring in scrap, although this will depend, case-by-case, on the permission of my father. As an aside, I wonder if silver was ever hot-forged during the middle ages? A page about Garry Noffke on Ganoksin says that he uses a special alloy to hot-forge because sterling silver didn’t work too well. Exploring historical silver alloys will be a post in itself, I think.

Ideally, I’d love to work with gold, but cost will simply make this prohibitive for experimental purchases. Where I will be able to work with gold is through my modern jewellery employment, by integrating older casting techniques to contemporary work. In this case, I’m likely to be using 18ct yellow gold, as this is the main material used by the business (well, we use a lot of platinum, but I don’t think that platinum was used until much later in history). I won’t need to use gold at my home workshop, but for reference, it’s top melting point is 960C.

The final alloy that I might use is pewter, which has a much lower melting point; according to Wikipedia, this is between 170C and 230C. I’d only be using this if I failed with everything else, so I’ll leave discussing it until I actually need to do it.

One further material is relevant when it comes to jewellery – ceramics. Whether for crucibles, moulds or for components of furnaces, I’ll need to use clay and similar materials, so the temperature of my furnace will need to reflect that. Campots arcaeoceramics (sp?) seems to suggest firing temperatures of up to 1000C, which seems to be the same range as jewellery. Convenient? Perhaps. But maybe this effected the  way that pottery and jewellery developed.

So, I need fuel and a furnace that can reach 1000C.


Laurie K February 19, 2010 at 20:52

The bigger question is WHAT WILL YOU MAKE!

Jamie Hall February 19, 2010 at 21:02

That is quite a good point, actually! I hadn’t thought of it in those terms – I think there will be a separate post on that.

Short version, though, is starting with simple castings of pendants or rings, then moving onto to torc bangles. After casting, I’ll look at forging, initially I’ll try making some rudimentary bullion products, and then move onto forged torcs and rings.

Those are all basic, and fairly generic techniques, so once I’ve proved myself able to make anything decent, I’ll have a look at replicating items from hoards and burials.

Michael Johnson February 22, 2010 at 02:18

Alloys of silver and copper were common since the Egyptians. So, I would suggest sticking to Sterling. These old alloys probably came close to that, give or take a few percentages. The term “Sterling” actually comes from the Germans, but it’s alloy percentage of 92.5 was usually the goal of most other silversmiths through out history. The silver just works better at that alloy.

Check with some of the Alchemist websites. Some have actual scans of ancient documents of these old alchemist metal workers. Just shy away from the alchemy sites that are more like a cult than metallurgists. Alchemists and their networks were how the arts of silver and gold were spread. All of that lead into gold crap was more of a side note in history that the church made a bigger deal about than it really should have ever been.

Plus keeping with sterling takes away the hassle of keeping your metals separate, and you can buy pre-alloyed sterling in a pinch :o)

Martin Smith February 24, 2010 at 16:20

You have contacted my brother about charcoal, I was reading this post and remembered an alloy the Egyptians used which Michael might be eluding to. Electrum was common in ceremonial jewelry, ceremonial septres and coinage.
It is interesting that there would have been a proportion of contaminant metals that would have affected the melting point.
Here is the wikipedia article

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