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Gold-filled is not an alloy. It is a layered material constructed in two or three layers.
The core metal is jewelers' brass; though, in the past, sterling silver was sometimes used instead. Single clad gold-filled has all the gold content in a single layer on one side. Double clad material splits the gold content into surface layers on both sides of the material. The gold alloy is bonded to one or both surfaces of the brass core with heat and pressure. The bonded raw material is sold as a sheet or wire to jewelry manufacturers for use in designs.
Gold-filled jewelry supplies are legally required to be 5% or 1/20 gold by weight. This 5% is described by the karatage of the gold alloy on the surface. Most material is 12kt or 14kt gold-filled. It is most accurately labeled with the karatage, the "/" symbol, and then 20 to reflect this construction. Products are identified as 14/20 or 12/20 Gold-Filled; alternatively, 14kt or 12kt Gold-Filled are also acceptable as long as you use the entire phrase. Quality stamps are abbreviated to 14/20 GF or 12/20 GF.
Is gold-filled the same as gold plated?
No, gold plating is a minuscule layer of solid gold applied to a brass base. The plating does not compose any measurable proportion of the product's total weight. It is estimated to be 0.05% or less of the metal product. Gold plating can wear off quickly and expose the brass base product. It does not stand up to heat, water or wear over time. By comparison, gold-filled contains 5% gold by weight. All the gold is on the surface which offers product protection from tarnish and wear.
To make gold-filled pieces, the core metal is sandwiched between two layers of gold alloy which is then heated and passed through a roller several times - a process that both bonds the metals together and thins the sheet out.
To make gold-plated pieces, an electric current is used to negatively charge the base metal and positively charge a solution containing gold ions. The positive gold ions are attracted to the negative charge of the core metal, slowly forming a layer of gold on top of the core.
Can gold-filled tarnish?
Yes, it can, but it takes a rare set of circumstances. Gold-filled jewelry supplies are a lifetime product because the gold layer bonded to the brass core is quite thick. However, in rare instances of extreme sulfide exposure, it can blacken. This has only occurred a handful of times over our decades of experience:
Foreign transit through extremely polluted shipping docks has caused the product to blacken on several occasions.
Products stored in nail salons with high levels of chemical sulfide fumes are at risk of blackening.
A fire where the structure filled with smoke caused blackening
These are extreme conditions. However, it has made me think twice about breathing the air in nail salons. Gold-filled usually just requires light surface cleaning with an untreated cloth or mild soapy water.
Can you be allergic to gold-filled?
Individuals who have skin reactions with gold alloys will also react to the gold alloy layer on the surface of gold-filled. Some people's body chemistry will cause their skin to blacken or develop a rash when they wear certain metals. I am one of those people and on certain days, my fingers will turn black all around my 14kt wedding band. Rarely, an individual's body chemistry may darken the metal as well.
Suggested Cleaning Methods
Mild soapy water and a toothbrush - a child's soft toothbrush and a mild detergent is the perfect combination for cleaning golf-filled jewelry. The detergent can remove residue or fingerprints from the item, and still leave it shiny and bright when it's done. Be sure the toothbrush is soft or it may scratch your piece!
Soft cloth - using a clean, soft cotton cloth is an ideal way to polish your gold-filled pieces. A soft cloth will not scratch the surface. There are treated jewelry polishing cloths, such as Brilliant, that work well; however, some chemicals are not recommended on gold-filled items so double check that they are safe to use. Do not leave chemicals on your gold-filled. Always rinse and polish again with a soft cloth to remove residue.
Ultrasonic machine - quickly clean your pieces with an ultrasonic machine. Be sure you don't leave the pieces in for too long (check every 2-3 minutes) but most importantly make sure that the cleaning solution is safe to use with gold-filled items! Rinse with water and dry with a soft cloth when you are finished.
Original article by by Katie Hacker