A Different Frankish Ring

A friend of mine commissioned a custom ring for his lady. After talking a little bit, I sent him a photo of this one from The Met, and asked if something similar (with his stone preferences, and in silver) would work, and he said yes! So I got to work. We had discussed using a 6mm stone for the center, and two 4mm stones for the sides, so I made those bezels, and then used 24 gauge silver wire to make the twisted wire detail. Four granules done, and I was ready to lay out all the pieces on a back plate. But wait! This setting ended up too large for a ring like the photo. I should have paid more attention to the original dimensions. 6mm is roughly equal to 1/4". Which is the overall width of the original bezel. Erego, the original center stone must have been closer to 4mm, with the side stones at 3 or 3.5mm.

Progress pics:

Since I already had the stones in hand, I sent my friend a progress photo and explained the issue. I gave him a few options, and he chose to just turn the setting so that the lengthwise axis will run parallel to the finger, rather than perpendicular to it. Perfect! That's further from a replica of the original piece, but it's still in keeping with the design aesthetic of medieval jewelry.

I ended up needing to remake the setting because there was a gap between the first and second bezels that bothered me. The final setting still isn't perfect, but my friend okayed it. 

After soldering all the new pieces onto the back plate, and finishing it, I chose to use the same split shank attachment seen in the original Frankish ring I remade. Given the extra size of the setting, the additional surface area was desirable.

Setting the 4mm stones proved a bit of a challenge, especially because their bezels were on the tall side. I could have put a small ring of silver wire underneath each stone, to raise it up a bit, but I chose to just muscle through. Overall, all three of us are very pleased with the outcome! This is definitely a style I want to play with some more. 

Soldering Research Continued, and Some Future Plans

On first read, Theophilus' treatise "On Divers Arts" is on the complex side, and he includes a lot of steps for things that sometimes border on mysticism. The most famous example of nonsense is his assertion that the urine of an old, fasting goat, or alternatively, a small redheaded boy, is most effective for quenching metal in hardening. His information on soldering isn't quite that outlandish, but it is rather complex.

Let's start by trying to demystify his instructions on soldering for silver. He starts with a recipe for solder that's a simple 2:1 silver to copper alloy that stays consistent through Cellini's treatise on goldsmithing, and isn't too far off from modern solder. So nothing strange there.  Then he says to take argol (the sediment found in bottles wherein the best wine has been stored), wrap it in a cloth and burn it, blow away the ashes of the cloth, and then grind the burnt argol in a copper pot, together with salt and water to make a paste. He then instructs the goldsmith to spread this paste on his joints, and sprinkle shavings of the pre-made solder over it.

So "argol" is also called wine stone, or tartar, and is a crude form of potassium bitartrate. A relatively refined version of potassium bitartrate is found in baking: cream of tartar. Armed with this information, I have to wonder if ordinary cream of tartar, mixed with salt and water to make a paste, would act as a functional flux, when used with modern solder. So this is an experiment I intend to undertake in the very near future.

Secondly, let's look at his instructions on "Solder for Gold". Theophilus instructs the goldsmith to make lye using beechwood ash, and then to strain the lye water through the ash again, to thicken it. You boil this and reduce it by 1/3, mixing in with it some unspecified amount of soap and pig fat. Once cooled, he instructs us to strain it and store it in a specially described copper pot. Leaving that aside for the moment, he then tells us to take a flat, thin piece of copper, wet it, and then rub it with salt. Put the copper in a fire until it is red hot and then quench it in clean water. Continue this process, collecting the burnt copper oxides in the clean water until you have a quantity of such. Then pour off the water and allow the resulting powder to dry, and then grind it with an iron powder. Put the powder on coals and burn it again, and then grind it again. (This gets a bit repetitive.) Then add soap to it, mix it carefully, burn it again, and grind it again. At this point, pour the lye into the vessel with your copper powder and let it boil and reduce for "a long time". Once it's boiled and cooled again, pour it back into the copper vessel you were previously storing the lye in. This is its storage container. Theophilus tells us to add several pieces of copper to this container, and to stir them together with the liquid.

At no point in the instruction does he mention making a separate solder material. This resulting acidic soapy copper oxide is the only material he goes on to reference in soldering gold. The very helpful editor provides a note, at least in my Dover edition, explaining that this is a somewhat convoluted version of a process that was used for hundreds of years, and that Cellini describes a similar process, as well. The science is this: copper oxides are mixed with a paste flux, and applied to the metal joints. When heated, the copper converts to metallic copper, and, being in contact with the silver or gold, it immediately creates an alloy at the contact spot that's got a lower melting point. It creates a fusion of the materials without requiring the fine metal to get to its own melting point. Fusing at that point becomes less precise in nature, and does not result in the finely detailed filigree and granulation work that we see in extant examples. Fusing at the lower temperature created by the copper alloy preserves the delicate detail work.

Cellini's recipe for this is to use verdigris, mixed with sal ammoniac and borax. Which supports my assertion that the fundamental parts required to function in this way are copper oxides and flux. So in a slightly farther future experiment, I intend to acquire some copper oxide and sal ammoniac (I am not prepared to make my own lye at the moment), and see what I can accomplish!

Medieval Methods vs. Modern Methods: Soldering

Much like sewing, not a whole lot has changed in the last few millennia. Soldering has been a technique in use since early on in the process of metalworking. Give or take 5,000 years. And metal, like fabric, can be made into hundreds of thousands of different things, but the methods of making those things are fairly limited, and defined by the material's properties. Metal can melt. Metal can bend. Metal can harden and soften. Metal is reactive to some acids. Metal can be mechanically fastened to other materials. And metal can be melted and "fused" onto other metals or itself (welding), or a metal with a lower melting point can be used like glue to fuse two other pieces of metal. Which is soldering.

By its nature, metal has to be clean and free from oxidation in order for it to be properly soldered. Flux is what we use to prevent oxidation, and there are several different chemical forms of flux, with the simplest being a borax cone that gets combined with distilled water in an unglazed ceramic dish. Borax and its chemical properties with respect to metal were known and can be documented in medieval metalsmithing practices. Interestingly enough, while Theophilus of Edessa mentions the use of borax in "On Divers Arts" (12th century), he separately provides a recipe for flux to be used in soldering silver. It involves the resin left at the bottom of wine bottles. He also provides a recipe for soldering gold, using lye, salt, and copper, but mentions that it can be used to solder both gold and silver. Cellini, in the 16th century, simply indicates borax.

Heat must be used to melt, weld, fuse, or solder metal. Modernly, most people use torches, with working pieces placed upon heat-reflective fire safe surfaces. I, and many people, use a simple charcoal block. There are other options available, including ceramic honeycomb, vermiculite, or magnesia blocks. Now, specifically, I work on a dense charcoal block made specifically for this use, that sits on a vermiculite block, that sits on my desk. The vermiculite block is bigger, and acts as a secondary, heat-safe workspace for things to be set upon safely, and to act as a safety if sparks fly. Charcoal doesn't act as a heat sink. It reflects heat back on your piece, and it can, by its own nature, ignite and smolder, so working with it on a secondary heat-safe surface is important. Some people choose to douse or quench their charcoal blocks after use.

That said, charcoal is indispensible to the discussion about medieval metalwork. Charcoal fires can get as hot as 2110'F. In a forge, with oxygen added to it via bellows, a coal fire can get as hot as 3590'F. Charcoal fires are how medieval metalworking was accomplished. For reference, the melting point of silver is 1,763'F, the melting point of gold is 1,948'F, and the melting point of steel is 2500'F.

Theophilus describes building a forge on a bed of sand with charcoal, and then for a soldering process, placing the pieces to be soldered on the charcoal, supporting them with more coal if needs be, and then building up charcoal walls around the piece, so that it can be heated evenly all the way around. Gaps were left so that the piece could be observed through heating. The coal fire was fed oxygen with bellows until it became hot enough for the solder to flow, and then the charcoal was removed and the piece was taken off the heat.

Ultimately, while a few of the tools have gotten better, and the visual aids and artificial lighting we have modernly make fine detailed work easier, the actual processes of metalworking have been virtually unchanged for millennia, which is pretty danged cool, if you ask me.