Jewelry: Step by Step
As you might expect for an art this ancient, there are many different techniques for forming precious metals and gemstones into jewelry that you can wear.
Each method has advantages. For example, some jewelry is manufactured using a technique called die striking: sheets of metal are stamped into shape under enormous pressure using an engraved metal die. Because the dies and machinery used are expensive, die striking is generally used to manufacture large numbers of a single style. On the other end of the spectrum is hand fabrication, which is, as you might expect, the labor-intensive making of an individual piece of jewelry by hand, using tools and heat to bend and shape the metal.
The majority of jewelry created today is made using lost-wax casting, an ancient method updated with modern materials so that it can be used to make one or many copies of a jewelry design. We will take you step-by-step through this process to show you how the jewelry you enjoy was crafted.
Step 1: The Sketch
Although some designers, sculpturally oriented, might carve a design into being, almost all jewelry begins with a sketch of piece of jewelry. Although some computer programs now exist to standardize this process, many designers still prefer pencils. Whatever method they use, designs are often drawn from different perspectives since almost all jewelry is three-dimensional in concept.
The sketch also needs to be in proportion, so that the size of the stone can be calculated. Most cast jewelry is set with standard size gems, so the designer needs to plan which of these sizes will be used. Sometimes the design is created with variations for different stone sizes and shapes.
Step 2: The Model
The sketched design is then carved into being, usually in special jeweler’s wax. This model must be perfect and flawless in every detail, since the final piece will only be as good as the model. The tricky thing is that during the process of turning this model into a final piece, the scale will shrink slightly, depending on the materials used. So the model maker needs to make sure that the original wax model is slightly larger than desired: but large just the right amount so that the setting and the ring, for example, will be the right size after shrinking for the stone and the finger it’s being made to fit. To help the model maker achieve perfection, there are lots of tools, including pens that precisely add wax where desired, tools that carve it away, and standard size wax molds for the band and setting basket, which can be used as is or modified.
Step 3: The Rubber Mold
The original model is encased in plaster-like investment, which is specially created for jewelry making. After the investment sets, the encased wax model is burned away in an oven, leaving a jewelry shaped void in the hardened investment. That space is filled with silver, forming a slightly smaller duplicate of the original wax design, which is polished to perfection. The silver master model is then packed into a fat sandwich of special mold rubber and squeezed tight under high heat and pressure until it forms a solid block. The rubber forms itself around the master model, creating a perfect three-dimensional impression of the piece of jewelry. The rubber is cut in half to remove the silver master. Then the rubber is put back together and hot wax is injected through a hole in the rubber to fill the ring-shaped space inside, forming a wax reproduction of the master model (but a bit smaller.)
So all these steps have taken us back where we started: with a wax model of the ring, which is checked again to make sure it is perfect, and any seam mark removed. However, now that there is a rubber mold, any number of these waxes can be created. When it starts to lose detail, a new rubber mold will be created from the master model.
Step 4: The Wax Tree
To finally turn wax into gold, a number of wax models, usually 10 or 20 are placed on a large branching wax tree. Positioning each piece on the tree must be done carefully, thicker pieces will go on the bottom, thinner on the top and the joint where the piece is joined to each branch must be positioned in a thick place in the design, where there is no detail, like the back of a ring. When the tree is complete, the whole wax structure is placed in a flask.
Step 5: The Plaster Mold
After the wax tree is placed in the flask, a special liquid plaster called investment is mixed and poured over the tree to encase it all in plaster. A vacuum is used to remove any air bubbles from the liquid investment. Like the single mold of the original model, after the investment hardens, the wax is burned out, leaving a branching tree hole to be filled with molten metal.
The mold is placed in a vacuum chamber before it hardens to remove any air bubbles that could cause problems down the line. Once the plaster mold hardens and cures, it heated in a gas oven to melt out all the wax, leaving a hole in the plaster that is an exact replica of the branching tree of wax jewelry.
Step 6: The Pour
After the mold is hardened and burned out, grains of gold alloy, or mixture of gold and other metals added to it, are melted in a separate casting machine furnace. Most jewelry in the United States is 14k gold, with is a mixture of 58% gold with silver and copper. 18k gold is an alloy of 75% gold, also mixed with silver and copper. To make white gold, nickel or palladium is added to the alloy. To make rose gold, extra copper is used. When the metal is the correct temperature, it is poured into the hardened plaster mold with the tree impression. Sometimes it is spun to make sure that the molten gold quickly fills the topmost branches of the tree, with every detail, before it starts to cool. After the gold hardens the mold is cracked and the golden tree is removed. Individual pieces are separated and sent for finishing.
Step 7: The Pre-Polish
First, the jewelry has to be removed from the branch, or sprue, that held it to the tree in the mold. It is then is tumbled into smoothness, sometimes sanded, lapped to make edges crisp, and then buffed by hand on a polishing wheel. Of course the final piece is checked again to make sure that no errors were introduced during the casting process. In particular, quality controllers check for any signs of porosity in the casting: little grains, voids, or bubbles that indicate that the hot gold didn’t properly fill the mold, creating a strong single unit of metal. Porosity can be an indication of weakness in the metal’s crystalline structure.
Step 8: Assembly
Now that all the jewelry pieces are cast and pre-polished, they are ready for assembly. Here is where earring posts are added to the earrings, die-struck heads to hold gems are added, or bracelet links are attached. To do this, a special gold alloy that melts at a slightly lower temperature than our cast pieces of jewelry is used to solder or weld these gold pieces, called findings, into place. Once all the soldering is completed, the jewelry creation is ready to move to the gem setting stage.
Step 9: Setting Gems
Now that the jewelry piece is pre-finished, it’s time to add the sparkle. Gem setters are the skilled craftsmen who firmly capture gems in metal. In so doing, they must balance several concerns. First, they must work carefully and slowly so they don’t damage the gem. Metal fabrication is often done with heat but the setter can’t expose most gems to an open flame because it might damage them. Second, the setter often must adjust a setting to the individual outline of the gem. Even a carefully scaled model might result in a setting that must be adjusted to fit properly. And the gem must be held squarely and securely in an even plane with all the other gems in a piece. The easiest setting is the prong setting. In this case, the setter just needs to carefully notch each prong with a tiny cutting burr and then bend the prongs over the gem to hold it firmly in place. More complicated settings are bezels and semi bezel, which have collars of metal to surround the gem. These settings are difficult to adjust if they don’t fit exactly. The bezel should be even all around the stone, with no gaps. Now accent stones, often diamonds, are added. These are sometimes channel set in a row with the gems suspended between two rails in a channel of gold. When the setting is done well, the setter’s work is invisible: the gem is perfectly placed to shine.
Step 10: Final Touches
Now the piece of jewelry is finished and it only needs a light final polish to bring out the luster and shine of the gold. This is done by putting fine red jeweler’s rouge on a soft cotton cloth and buffing the piece by hand, making sure that all the details and highlights shine.