Tag Archives: Metal casting

Choosing Which Metal To Use – Part 2

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Last time we talked about choosing true bronze in order to get the look, feel, and functionality that we see in many pre-1600 pieces. But there is at least one metal that I generally avoid like the plague in my workshop – lead. Lead was widely used in many pre-1600 items (for that matter it wasn’t banned from house paint in the US until 1978). When we look at period examples of inexpensive jewelry, it is often made from lead, tin, or an alloy with lead.

This example, of a lead cross pendant from Egypt, is typical of some of the less expensive jewelry that would have been made for ordinary people.

Lead can also be used as a decorative element in jewelry, including niello and leaded enamels. Niello is a black substance that can be fused to the metal in a piece of jewelry to create a contrasting design. If you are interested in the details of how niello is made and used, please visit my blog on this topic.   The Anglo Saxon’s were masters in the use of niello. The black stripe up the middle of this Anglo-Saxon brooch is niello (and so is a lot of the tracery on the Sutton Hoo pieces).

Prior to 1990, Thompson Enamel, which produces a considerable percentage of the enamels used by both artists and industry, contained lead. Many companies still make leaded enamels. And it is safe to say that most enamels that were used before 1600’s would have contained lead. Lead makes the enamels very stable and gives them good flow properties. For more information on enamels, here is the link to one of my blogs on enamels and how they were used (I mentioned it last week, too).  And yes, I do sometimes use leaded enamels.

Lead, being a naturally heavy substance, was also used for many practical purposes like this steelyard weight.  The Bronze weight was cast as a hollow piece and then filled with lead until it was the desired weight.

Spindle whorls are another excellent example of an item was very frequently cast in lead. I own several lead spindle whorls, all of which were found in England. Lead, being a rather soft metal, is relatively easy to damage. Two of the spindle whorls in the bottom row of this picture are excellent examples of this. The far left whorl has been compressed slightly, and the spindle whorl that is the second from the right shows a significant gouge, probably from a plow.

spindles

Lead can certainly be used and worked in a safe manner, but legally there are a lot of issues. Every state has different rules about how much lead is legally permissible in jewelry, especially in jewelry that may be used by children. When I first started making jewelry I sat down to read all of the different regulations for the states that I was planning to merchant in. It didn’t take me long to decide that it was simply easier to avoid it. Whenever pewter or lead is called for in jewelry or other accessories, like spindle whorls, I simply use a good quality unleaded pewter from a reputable supplier.

Next Time: Are there any other issues with metal that should be considered?

My Casting Process Up Close – No It Is Not Instant!

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I have been chatting with several customers lately at events, and it has become painfully obvious that some of them think that the casting process is almost instant, and that the cast pieces arrive looking as lovely as a shiny new penny.

Not really.

I was trying to figure out where they may have gotten this impression from. Maybe they watched an edition of “How It’s Made” where a giant machine spits out polished pieces, or maybe they have seen pewter casting.

So I thought about the Pewter Casting for a while. I do a little pewter casting for some of my reproduction spindle whorls. The originals were lead, and I am just NOT going to go there, so I use lead free pewter. I also make a few Pilgrim’s badges in pewter and bronze.

Cast Pewter pieces come close to looking like that new penny that we talked about, at least a lot closer than bronze or silver do when they are cast. This picture gives a nice perspective on casting simple pewter pieces. The original soapstone mold that I created for the scallop shell pilgrim’s badge (Santiago de Compostela in Spain), is on the far left. An “almost” cast ( the loop is incomplete and the “wings” on the top of the shell are not squared enough) shows what a fresh casting might look like. Above this is a row of six small spindle whorls, one of which still has it’s sprue intact. The larger spindle whorls on the right side show what flashing looks like (that wobbly bit sticking out on the edge of the spindle whorl).

pewter casting

OK, so let’s look at the process objectively. The mold is clamped, and the molten pewter is poured into the mold and allowed to cool. After three or four minutes the cast piece can be taken out of the mold. It will still be hot, especially if it has some bulk, like the spindle whorls do. Depending on the temperature of the room and workbench, a five minute wait is probably a good idea. Then I use a pair of sprue cutters to cut off the sprues. You can see where the sprues have been cut off on both the large and small spindle whorls. I then remove any flashing around the edges of the piece, either with a file, or a wet sanding machine. During this process the remains of the sprue are also removed. I then check any interior “holes”, like the interior of the loop on the scallop and the center hole on the spindle whorls for flashing, and remove it. Now the piece is ready for a quick polish. Twenty minutes in a tumbler with steel shot and burnishing compound will remove any oxides and give the pewter a nice sheen.

polished pewter

Shiny! This is what the polished pewter looks like. It is really not a complicated process, but even something as simple as pewter casting is definitely not instant.

Next Time: What Happens When We Cast Bronze

The Way That I Cast : Lost Wax Process- Part 6

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Last time I discussed the most basic casting set-up that I could think of, that was likely to create successful results. I also mentioned the biggest problem with this system – your model is destroyed in the process.

The biggest question about casting that you really need to ask yourself is “Is this something that I want to do just once, or twice, or is this something that I want to be able to continue to do for the foreseeable future?” And along with this question is another important issue – “Do I feel that I have to do all the parts of the casting process myself? Or can I “farm out” some, or most, of the process to a professional?”

So what sort of options do we have? Well, the first thing that comes to mind is to solve the problem of destroying your model yourself. You can make a mold of the model so that you have the option of making copies of the model if you want to make more items, or if the casting process fails. There are a lot of very user-friendly Room Temperature Vulcanizing compounds out there that do not require any special equipment. I have more complex equipment, but I still often use RTV compounds to make molds. Here are a couple of my molds.

RTV molds

What if you really enjoy the idea of making the model, but you really are just not up to doing the casting yourself? Well there are reputable companies in the US that will take your model and cast it for you. They will generally want to make a mold of the model as insurance against a failed casting. You can arrange to receive the mold yourself, along with the cast piece, or have them archive the mold. Be sure to understand all of the costs, who owns the mold, and whether they archive it, or you get it back.

I do not recommend sending a model “offshore” to places like Pakistan or China. Factories in these areas usually specialize in large quantity production. They often own the molds, and you may not get your master back. Your legal recourse if you are not pleased with the results, is limited, and you will have to pay import fees. I do know people who have their business production done off-shore. The Pakistani company is casting bronze pieces and their minimum order is 1000 of the same pieces. I was not impressed with their quality. The Balinese company is casting silver. They will cast much smaller numbers of items, but still not ones and twos, and their quality is very good.

But back to getting work done in the US. As long as you understand the fees and rules you should be fine. Taking this to the extreme, there are shops that will do custom casting, from design to finish. The most technologically savvy shops will have computer design capabilities that will use 3D printers to create the original model. I have seen them in action, and it is amazing. Small shops may also be willing to do wax models and cast very limited quantities.

I hope that this blog gives you some ideas about your casting options.