Mixing gold with other metals is a common practice in jewelry making and metalworking. It allows jewelers and artisans to modify the properties of pure gold, which is relatively soft, for use in different applications. The most common approach is alloying, which combines gold with other metals like copper, silver, nickel, zinc, and palladium. Alloying gold modifies properties like hardness, durability, color, and melting point. This allows gold to be tailored for uses like jewelry, dental fillings, electronics, coins, and more.
Why Mix Gold?
There are several reasons why jewelers and metallurgists mix gold with other metals:
- To increase hardness and durability – Pure 24K gold is very soft which makes it prone to scratching and denting. Alloying it with metals like copper and silver hardens the gold for use in jewelry and other applications requiring durability.
- To modify melting point – Pure gold has a melting point of 1064°C. Mixing it with other metals can lower the melting point, making it easier to work and shape.
- To change color – Alloying gold with metals like nickel, zinc, and palladium can produce white gold and other color variations.
- To reduce cost – Alloying pure gold with cheaper metals reduces the overall cost of the final product while still retaining the desirable gold properties.
- To improve workability – Some metals mixed with gold improve its malleability and ductility, making it easier for artisans to work and shape the metal.
In short, mixing gold alloys allows for tailoring the properties of gold to suit specific needs. Jewelers can select metals to mix with gold based on the desired hardness, color, melting point, durability, and cost.
Common Gold Alloys
Some typical gold alloys used in jewelry making include:
- Rose Gold – Gold alloyed with copper and silver, producing a pinkish hue. Typical composition is 75% gold, 22% copper, 3% silver.
- White Gold – Gold alloyed with nickel, palladium, or silver creates a silver-white color. Typical composition is 75% gold, balance nickel and other white metals.
- Green Gold – Gold alloyed with silver, and sometimes cadmium, produces a greenish color. Typical composition is 75% gold, balance silver and other metals.
- Red Gold – Gold alloyed with high copper content (25-30%) creates a red color. 18K red gold is 75% gold, 25% copper.
- Blue Gold – Made by adding iron during the alloying process, resulting in a blue to purple tint.
The karat designation indicates the gold purity in parts per 24. So 18K gold contains 18 parts gold and 6 parts alloy metals, which is 75% pure gold. Common purities for gold alloys are 24K (pure), 22K (92%), 18K (75%), 14K (58%), and 10K (42%).
Alloying Process
The basic steps for alloying gold are:
1. Calculate the percentages of each metal based on the desired karat weight.
2. Weigh out each component metal to meet the formulation.
3. Melt the metals together in a furnace or crucible at around 1900°F.
4. Mix the molten metals thoroughly and pour into ingot molds to solidify.
5. The alloy ingots can then be shaped as needed by processes like rolling, forging, extruding, etc.
6. Anneal and work harden the gold alloy for desired hardness and malleability.
Proper mixing when melting is crucial for uniform distribution of metals and consistent properties throughout the alloy. The molten metals are often stirred mechanically or with a torch.
Why Metals are Chosen for Mixing
Some key factors guide the selection of metals for mixing with gold:
- Properties – Metals are chosen to modify gold’s hardness, color, melting point, and workability per the desired end use.
- Cost – Less expensive metals like copper, nickel and silver are added to reduce cost of the final alloy.
- Availability – Metals need to be readily available in the necessary purities and quantities.
- Safety – Toxic metals like lead, arsenic and cadmium are avoided, especially in alloys for jewelry.
- Color Compatibility – Metals like copper, silver, and zinc blend well color-wise with gold.
- Mixing Ease – Metals are considered for their atomic structure and miscibility for blending smoothly with gold.
Common choices are copper, silver, nickel, zinc, cadmium, tin, platinum, and palladium. These alloy relatively easily with gold, produce desirable properties, and have colors harmonious with gold.
Effects of Common Alloying Metals
| Metal | Effects on Gold Alloy Properties |
|---|---|
| Copper |
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| Silver |
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| Nickel |
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| Zinc |
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| Palladium |
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As illustrated, careful selection of alloying elements allows jewelers to modify gold’s properties for the desired application.
Steps for Mixing Gold Alloy Jewelry
Here is an overview of the typical steps for mixing gold to create custom jewelry alloy:
1. Design the jewelry item and determine required properties – hardness, color, etc.
2. Calculate the formulation percentages based on target karat weight.
3. Obtain metals for alloying – gold, silver, copper, nickel, etc.
4. Weigh out each component according to formulated percentages.
5. Melt the components together in a crucible or furnace at around 1900°F.
6. Mix thoroughly to fully blend the metals into alloy.
7. Pour molten alloy into ingot molds and allow to cool and harden.
8. Shape and fabricate alloy as needed – rolling, forging, wire drawing, casting, etc.
9. Machine and polish jewelry piece as designed.
10. Anneal alloy if needed to soften for shaping.
11. Optional – apply plating, coloring, or protective coatings.
Proper mixing and blending when melting is crucial for even distribution of metals in the alloy. This helps achieve uniform properties and gold color. The molten alloy is typically stirred mechanically and re-melted multiple times. A metallurgist can advise on best mixing methods.
Conclusion
Alloying allows pure gold to be mixed with other metals to modify its properties for uses in jewelry, engineering, dentistry, electronics, and manufacturing. Carefully calculating the percentages of metals and thoroughly mixing during melting produces gold alloys with consistent properties. Common alloying metals are silver, copper, nickel, zinc, and palladium which allow tailoring gold’s color, hardness, melting point, durability, and cost. With the right metal combinations and techniques, gold can be transformed into specialized alloys meeting needs across many industries.
