Precious Metal Fabrication: An Overview of Gold Ornaments

Gold Alloys and Their Properties

Pure gold (24 karat) is too soft for most jewelry applications. It's therefore alloyed with other metals to increase durability and alter color. Common alloying metals include silver, copper, nickel, palladium, and zinc. The karatage indicates the proportion of gold present (e.g., 18k contains 75% gold). Different alloys result in varying hardness, ductility, melting points, and resistance to tarnish.

Basic Jewelry Manufacturing Techniques

Various methods are employed to shape and join gold. These include:

Casting: Molten gold is poured into a mold. Common casting methods are lost-wax casting and centrifugal casting.
Fabrication (Benchwork): Gold is shaped using hand tools and machines. This involves techniques like sawing, filing, soldering, hammering, and polishing.
Forging: Gold is heated and shaped using hammers and anvils. This strengthens the metal.
Stamping: Pre-cut shapes are pressed from a sheet of gold using a die and press.
Wire Drawing: Gold is pulled through progressively smaller dies to create wire.
Granulation: Small gold granules are fused to a surface.
Filigree: Fine gold wires are twisted and soldered to create intricate designs.

Soldering and Joining Techniques

Soldering is a crucial process for joining gold components. Different solder alloys with lower melting points than the base metal are used. Flux is applied to clean the surfaces and prevent oxidation during heating. Precise temperature control is essential to avoid melting the gold pieces. Laser welding is an alternative joining method that provides highly localized heat and precise welds.

Surface Finishing and Texturing

The appearance of gold jewelry is enhanced by surface finishing techniques. These may involve:

Polishing: Removing scratches and creating a smooth, reflective surface using abrasives.
Satin Finishing: Creating a matte or brushed appearance.
Texturing: Applying patterns or designs to the surface through hammering, engraving, or etching.
Plating: Applying a thin layer of another metal (e.g., rhodium) to enhance color, durability, or tarnish resistance.

Tools and Equipment

Jewelry manufacture requires a range of specialized tools, including:

Melting equipment: Crucibles, torches, and furnaces for melting gold.
Forming tools: Hammers, anvils, pliers, files, saws, and draw plates.
Soldering equipment: Torches, soldering picks, and solder.
Polishing equipment: Buffing wheels, polishing compounds, and tumblers.
Casting equipment: Casting machines, flasks, and vacuum degassing equipment.

Safety Precautions

Working with precious metals involves safety considerations, including:

Eye protection: Safety glasses or goggles to protect against flying debris and splashes.
Ventilation: Adequate ventilation to remove fumes from soldering and polishing.
Heat protection: Heat-resistant gloves and aprons to prevent burns.
Handling chemicals: Proper handling and disposal of acids, solvents, and other chemicals.