An Overview of the Metal Refining Process
Precious metals have many uses in industry and are widely used as investments and stores of value. But they are still mainstays of jewelry — in more complicated ways than you may realize.
The metal refining process plays a significant role in supplying the metal needed to shape an idea into a solid form. Understanding how the process works reveals the intricate techniques used to refine popular precious metals, such as gold and silver, and turn them into treasured heirlooms.
What Is Metal Refining?
In its simplest form, metal refining is used to purify an impure metal. When gold is used to make jewelry, it's mixed with other metals to create gold alloys, which are more durable and stronger than pure gold.
While a jeweler may decide to only use pure 24 karat gold in some of the jewelry pieces they create, it's usually not done due to the softness of gold and the vulnerability of showing wear and denting. This is why 14k or 18k white gold and yellow gold are usually the preferred materials.
Why Is Metal Refining Essential in Jewelry Making?
White gold isn't white when it's first mined. It's made up of pure gold that's been mixed with white-colored metals like silver, palladium, nickel and zinc. Mixing these metals with gold creates a more durable ring.
The final makeup of 14 karat white gold includes the combination of each metal below:
- 58.5 percent pure gold
- 12 percent copper
- 8 percent nickel
- 6 percent zinc
- 4.5 percent silver
A similar process is used to create 14 karat yellow gold. This alloy is made by combining 58.5 percent pure gold with 12.5 percent silver and 29 percent copper.
The value of gold is significantly higher than the other metals that are used to combine with it to form a piece of 14K jewelry. Refining pure gold and using it in a 14K ring helps a jeweler know the value of gold being utilized for the piece they're creating.
Platinum is one of the most durable and strongest metals used to make jewelry. It does not have to be combined with other metal alloys for strength, which is why it's often used to create delicate settings.
The Metal Refining Process
Taking an alloy, such as gold, and refining it can be done by using a chemical process known as aqua regia. It separates pure gold from the excess materials and metals. Using this refining technique involves inducing a chemical reaction that is corrosive. It's created by mixing concentrated nitric acid with concentrated HCl, which produces a red or yellow-colored substance that fumes when used during the refining process.
Aqua regia is Latin for "royal water." It gets its name for its ability to dissolve noble metals like gold. Since gold is mixed with other metals to make jewelry and naturally occurs as an alloy, using this refining process makes extracting pure gold efficient. Here's how the process works:
The alloy of pure gold and other metals is introduced into an aqua regia mixture where it's granulated and heated. A reducing agent is added to the mix to retrieve gold powder, which has been separated from the other metals. After it's washed and dried, it doesn't contain any other metals and can be used however a jeweler sees fit.
Safety Precautions
Using this refining technique does require taking a few safety precautions as volatile chemicals are utilized during the process.
Acids are capable of burning human flesh, and its fumes are toxic. Wearing thick rubber gloves, safety goggles, a rubber apron and a mask is usually the safest way to stay out of trouble.
The container used to hold the gold being refined will depend on the amount and size being used. Chemistry beakers are often used by individuals who are refining small portions of gold, and commercial units are used for the process when a refining company handles the work.
Adding the aqua regia solution and sodium metabisulphite to the container begins the reaction, breaking down and separating the gold from other metals. After a specific period, the chemical reaction will leave pure gold behind.
Extracting the gold from the chemical solution requires the chemicals to be removed and stored for future use. This should leave the gold used for making jewelry in the bottom of the container. Rinsing the gold with pure water will help get it ready for use in making rings or other types of jewelry.
Shaping Refined Precious Metals Into Jewelry
Once gold is pure, it can be shaped into casts and used to create a unique design. Silver is another precious metal often used for jewelry making, which uses a similar process that incorporates acid into the technique. Using this metal refining process is one of the least expensive ways to extract pure gold.
Gold electrolysis can also be utilized. However, a significant amount of gold is lost during this process, which can make it expensive.
Having a process to handle this technique is essential if a jeweler is carrying it out independently. Otherwise, they can hand it off to a professional company that specializes in metal refining. This may be an advantage as other metals can be extracted, such as silver, which is also valuable.
This article is a guest post from the writers at www.commodity.com. I would like to thank them for contributing this informative article about metal refining. I hope you enjoyed reading it as much as I did!