Friday, February 15, 2008

methods of manufacture

We love teaching our clients about the crafting of jewelry. It is an extensive, broad, topic. Here are a few words on each of the basic methods. We welcome additional questions!

Regardless of method, one tenet holds true of the collections we feature: none are mass-manufactured. One of the signatures of mass-manufactured pieces is that they lack the luxurious weight and heft of a finely-crafted piece. This is because competition in the "world of the typical" is very stiff, and mass-manufacturers will do whatever is necessary to get the price of their pieces down. That means cheap, third-world or developing-world labor, lightweight mountings, and lower-quality gems.

But don't take our word for it. Go ahead and hold a piece of chain-store jewelry, and see how it feels. Then come check out ours.

handcrafted

This is a term that gets abused a lot in our industry. Actually, the Federal Trade Commission (FTC) has a definition for the word "handcrafted" as it pertains to jewelry. To paraphrase, for a piece of jewelry to legally be considered handcrafted, the piece must be created from solid metal (as opposed to molten/liquid metal, which is how most precious metal jewelry is produced), using hand tools and a hand-held torch only.

Very little jewelry is handcrafted. Alara is proud to produce a number of lines that represent this "highest form" of jewelry craft.

cast

The great majority of precious metal jewelry (and in some cases, titanium and steel jewelry, as well) is manufactured by casting. Some folks understand this process quite well, thanks to a high school or college metalsmithing or sculpting class. For most, it seems quite the mystery. Here's a quick primer:

The most widely casting method for jewelry is called the "lost wax" casting method. You will not understand why it is called "lost wax" until pretty much the end of the description below.
To begin, a prototype of the finished piece you would like to have is made out of wax or special resin. The most common method for custom jewelry is that a prototype is carved, using hand tools, out of a hard wax. Other methods are to use a CAD/CAM application to produce a wax or resin prototype; or, in the event that the piece was made previously, and a rubber mold exists, that a wax model is extracted from that mold.

The prototype, produced by whatever means, is attached to a cylinder of wax at an obtuse angle. Also attached to this cylinder are any other prototypes that are intended to be produced in the same metal. This entire wax object vaguely resembles a thin tree trunk with a series of strange boughs coming off of it; hence its nickname: the tree.

The tree is suspended in a metal flask, and filled with a substance similar to plaster of Paris in consistency. This substance is called "investment."

The entire flask is put into an oven or kiln, and heated to various temperatures for specific periods of time. In this process, the investment hardens, and then the wax burns away, leaving a negative space the same size and shape as the original positive space. Hence, the "lost wax" casting method, as you "lose" the wax tree in the process of creating the vessel into which the molten metal will be injected.

Here again there are several methods by which the "negative space" of the investment can be filled with the liquid metal. In most small-scale production environments, the flask is either mounted onto a centrifuge, and the molten metal is injected into it through centrifugal force; or it is mounted on a vacuum caster, and sucked into it. Either way, once the molten metal "freezes" into solid, the investment is broken away to reveal the metal "sculpture."

The small pieces are clipped away from the "trunk" of the "tree," and the finishing process then begins.

assembly

This technique can be executed in a variety of ways, ranging from low-tech to high-tech. Basically, with such a vast supply of ready-made parts (called "findings" in the jewelry industry) available, a skilled jeweler can actually create a "custom" piece of jewelry by meticulously modifying and assembling such findings to make a unique piece of wearable art. Certainly more economical than handcrafting or custom casting, but not "do-able" with many designs.

Often, less skilled jewelers call their work "custom" when all they are doing is an assembly job. This practice is rampant. Beware-true custom is from the ground up, and all about you, not all about what findings are available to make something!

machined

While a technique used to some extent with precious metals, most machining is reserved for metals that are difficult to cast, such as titanium, tungsten, and stainless steel.

Machining involves starting with solid blocks of the metal, and then trimming away metal by removing material from a workpiece in the form of chips. Machining is necessary where tight tolerances on dimensions and finishes are required, and involves drilling, turning, milling, and grinding. These processes lend themselves best to straight lines and precise shape concepts, as opposed to organic or irregular lines.

After the piece is basically formed through chip formation, it must be finished to produce the desired finish.

die-struck

Used primarily when the desired finished pieces have relatively simple forms that can be pressed in a tool-and-die, die-striking is used in fine jewelry when a large run will be produced, due to the cost of producing the necessary hardened, tempered tool that makes the pieces.
Die-striking results in superior metal "structure" with zero porosity and defects, and is most commonly a method used for simple wedding bands, findings, and flat "stamped" pieces.

fired

Precious Metal Clay (PMC) represents a dramatic development in the handling of precious metals. PMC consists of microscopic particles of silver or gold suspended in an organic binder to create a pliable material with a consistency similar to modeling clay.

PMC can be worked with the fingers and simple inexpensive tools to create a vast range of forms and surfaces that would be unattainable or laborious with traditional techniques.When heated to a high temperature, the binder burns away and the metal particles fuse to form solid metal that can be sanded, soldered, colored and polished like conventional material.

Precious Metal Clay was developed by scientists working at the Mitsubishi Materials Special Products division in Sanda, Japan. After years of experimentation the first patents were awarded in the early 1990s with many additional materials joining the family of products. The principle ingredient of PMC is gold or silver, reduced to tiny flakes smaller than 20 microns in size. As a point of reference, it would take as many as 25 of these particles clumped together to equal a grain of salt.The other ingredients in PMC are water and an organic (naturally occurring) binder. After firing, the water and binder have completely burned away so what remains can be hallmarked as 999 silver or 999 gold.

No comments: