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Wood into Gold, and Other Tales of Transformation, Part 2

September 12, 2016

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In case you missed our last episode, cue the recap montage—A curious twist of fate; ancient rings are cool; never try to princess cut a black market kidney.

Or you can simply scroll down and read the entry itself …. It isn’t long.

So how many ways are there to make a ring? Probably countless ways, when you get into the particulars. But they all boil down to a small number of underlying strategies. 1. You can cast a ring. 2. You can build up a ring up from constituent parts. 3. You can do the opposite and carve a ring from a single piece of material (stock reduction). 4. Or you can beat the metal with a hammer and forge a ring. Did I miss any?

The rings I made involved three of those four strategies—casting, stock reduction, and forging.  My plan was to make her ring first then to make my ring from whatever gold was left. Most of the gold came from my old wedding band, a run of the mill 14k wedding band identical to the ring worn by countless guys the world over.

Reusing that gold was a practical thing to do, but as anyone who knows me could tell you, I’m not that practical. I used the gold from that old ring mostly because I liked the symbolism of it. And yes, I know—I can hear the tiny violins. The jeering. The sentimentality gestapo is knocking at my door. Yawn.

Once I had settled on the design for her ring, it was time to decide how I would make it. Casting made the most sense, at least for producing the basic shape. The problem was that I didn’t own any casting equipment. My hobby isn’t making things—it is reading about making things. So I had been reading for years about metal casting but had never done it.

When it comes to casting, there are two basic types, sand casting and investment casting (aka lost wax casting). I won’t go into much detail about investment casting—it’s the method I did not use. It produces a cleaner, more detailed casting than sand casting, but it also involves a lot more equipment, and I didn’t want to buy a bunch of expensive equipment that I might not use again.

Plus I didn’t need for the ring to be cast perfectly in every detail. I just needed to produce its basic shape. I had other methods I could use to refine the shape.

Enter sand casting. Sand casting is ancient. It requires very little equipment and is very simple. You create a pattern of the item you wish to cast. You use the pattern to create an impression in foundry sand. You then fill that impression with molten metal. Voila. You have a casting.

There is a bit more to it than that, but that is the gist.

 

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You can get started sand casting for under $100. Really you can get started for virtually nothing, if you are enterprising enough. I wasn’t, so I bought a rudimentary sand casting kit.

Wood was a natural choice for my pattern. I started with a 1″ diameter oak dowel and bored a 5/8″ hole down its length using a lathe. My wife’s ring size (5.5) pretty closely corresponds to a 5/8″ diameter hole.

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I then parted off the wood ring and carved and filed it to shape. A finer-grained wood such as maple might have been better, but oak worked just fine. I finished the pattern with shellac.

 

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With the pattern in hand, it was time to melt metal.

Almost….

Sand casting might not be complicated, but it is careful, detailed work. You spend most of the time doing what I can best describe as “crafting sand.” And yes, I realize that “crafting sand” sounds about as idiotic as a commercial for “hand-crafting” sandwiches. (Is handwork really in such decline that we now brag about “hand crafting” sandwiches? What other body parts might we use?). But at least with sand casting, it is quite true, even if it does sound odd.

It took me several tries to get a viable casting. A lot can go wrong, some of it obvious, and some of it not so obvious. On the obvious side, any imperfection in the sand gets transferred to the casting. That includes errant bits of sand that fall into the mold.

On the less obvious side? With sand casting, the only force pushing the molten metal into the mold is gravity. (Investment casting makes use of a centrifuge and forces metal into the mold using centrifugal force.). Gold conducts heat very efficiently, which means that it solidifies very quickly, and if it doesn’t flow fast enough through the mold, it will not produce a complete casting.

Several variables determine how fast the gold will flow.

The mold contains air that must have somewhere to go when it gets displaced by the gold. Therefore a series of vents are created in the sand around the perimeter of the mold. If the vents are not big enough, the air will not escape fast enough, and the gold will not flow fast enough.

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The three thin channels lead to vent holes poked through the sand with a wire. If you look closely you can also see bits of sand that have fallen into the mold and that will need to be carefully removed.

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This is what can happen if the venting is insufficient.

Just the opposite can can happen too. If the vents are too big, the gold can flow so fast that it drains into the vents and creates an incomplete casting that way.

The gold can also get hung up if you simply don’t pour it fast enough. Or if the lip of the crucible isn’t hot enough. Or if, in your haste, you pour the gold a tad off center.

It helps to pour more gold than is actually required for your casting. The added weight helps push the gold into the mold.

This is a sampling of the issues involved. Metal casting is a world unto itself. I was a mere tourist in that world for this project. And the metal casting was just part of the project. In fact, once the casting was finished, there was still more work left to do than was already done.

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It wasn’t perfect, but it was successful.

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The basic shape I was looking for. Essentially a starting point for the cold work to come.

There is a lot to go, and we are about to change gears, so let’s stop here for today. Tune in to Part 3 of this series to see this ring get completed.

My favorite part of the project is yet to come.

 

 

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