Before tackling how to solder gold-filled, let's review key issues about the raw material. I'll need to start with the basics or the construction of gold-filled. Then, I'll explain the complications you're sure to run across when fabricating jewelry. Once you have reviewed the necessary background information, we can really dive into soldering material choices and troubleshooting.
First of all, a little about gold. Pure gold equals 24 karats, which is too soft to make durable accessories; therefore, when you drop the percent of gold and add other metals to the alloy, a stronger metal is created. Below is a breakdown of the pure gold content found among the different karatages.
Percent of Gold:
- 24kt = 99.7% or more
- 22kt = 91.6%
- 18kt = 75%
- 14kt = 58.3%
- 10kt = 41.6%
By alloying gold with various metals, you can get an array of colors and shades. It is a beautiful, unique precious metal to work with. The standard gold color is a 14kt "hamilton" gold yellow color that is the most common in the jewelry field in the United States. 14kt yellow gold is 58.3% pure gold and the metals that make up the remaining 41.7% are usually 29% copper and 12.7% silver. Adding these two metals to pure gold makes it stronger, easier to work with and yet it still retains a stunning, soft yellow color.
What is Gold-Filled?
Gold-filled is a layered product. At the core of gold-filled items is jewelers' brass which is usually made up of 10% zinc and 90% copper. The gold alloy, such as the 14kt gold we previously discussed, is then bonded to the surface of that jeweler's brass using heat and pressure. This is a permanent bond and the gold alloy will never flake, peel or fall off.
This is important: By law, the total weight of a gold-filled item must contain 5% (or 1/20) of the gold alloy. If it contains less than 5%, it cannot legally be called gold-filled. We'll come back to that in a moment.
Construction of Gold-Filled Items
Gold-filled has a distinct layer of gold alloy bonded on top of a jewelers brass core. There are three different possible ways to layer the gold alloy.
- Single clad: has all of the gold alloy content layered on one side of the jewelers' brass
- Double clad: splits the gold alloy and layers it on both sides of the brass core
- Wire clad: the 5% gold alloy content is layered around the entire wire
Note: To read an in-depth article about the construction of gold-filled, check out our What is Gold-Filled? article. It includes a video that discusses the construction of gold-filled and rose gold-filled products.
Why Choose Gold-Filled?
If you don't have the funds to purchase solid gold items, gold-filled products are a great alternative. These products can last a lifetime, aren't affected by water or hot weather and they are tarnish-free under normal conditions.
Gold-filled findings are ideal for stamping and light metalwork such as texturing with a hammer. These techniques compress the metal, instead of removing metal from the surface such as engraving or diamond cutting. You should not use fabrication techniques that will pierce the surface layer. Remember, removing the gold alloy layer on the surface changes the ratio of the gold alloy vs. the brass core, and by law that gold alloy cannot drop below 5% of the total weight of the piece. Also, the exposed brass layer underneath is likely to tarnish and permanently discolor your jewelry piece. SHOP GOLD-FILLED JEWELRY SUPPLIES >>
What is the difference between Gold-Filled and Gold-Plated?
If you compare Gold-filled vs. Gold-plated article items, there is a significant difference between the two. Gold-filled must contain a total weight of 5% gold alloys bonded over a core metal, whereas gold-plated has to have 0.05%. That 0.05% is a thin solid gold plating, which is easily scratched and often wears through over time. One scratch on gold-plated products can expose the brass center. Gold-plating has a minuscule layer which results in a short lifespan and is unable to stand up to water and normal wear conditions like gold-filled products can. Gold-filled findings are not only quality alternatives to solid gold items, but they are also superior to gold-plated items.
Soldering Gold-filled Products
Gold-filled products are amazing, but now let's discuss the limitations when it comes to soldering. Think about it; applying heat to a layered material can distort or mix the separate layers. Soldering gold-filled products should not be attempted without professional training and proper jewelry tools. That being said, it can be done, however, it opens up a couple of possible problems that you need to be aware of.
We have a variety of manufactured gold-filled chains and findings and many have solder joins. These solder joins are usually done at the manufacturers using a laser welding machine which leaves a precise solder join without melting and mixing the alloy layers. These laser welding machines are expensive and the majority of jewelry studios don't own or have access to them. But with that kind of technology, soldering a gold-filled item is easy to do.
Note: There is no such thing as a gold-filled solder.
Soldering gold-filled items with a torch and gold solder is a completely different story. Since solder itself is an alloy of metals, there is no such thing as a gold-filled solder. The first thing you would need to do is to color match the solder with your piece using the same or a higher karat gold solder on your join. Since the top layer on gold-filled is usually 14 karat or 12 karat gold alloy, you will want to select a 14 karat or 12 karat gold solder.
Note: The higher the karat, the brighter the yellow because of the increased gold content.
One dilemma you'll run into is color matching your gold solder with your gold-filled piece. Since the surface layer of gold on gold-filled is usually 12 or 14 karat gold alloy, you should choose a solder that is color-matched to 14 karat gold. 14kt gold alloys mostly consist of gold, silver, and copper. They also usually contain the metal zinc (with tin and indium mixed in depending on the solder type and vendor). The metals found in gold solder are important because they cause the solder to flow at a lower melting point than the material you are soldering. However, since the percentages of the copper and silver differ in the solder compared to the gold alloys, those amounts affect the colors.
Note: Depending on the karatage of the solder, the alloys and the percentages will differ as well as the melt and flow points of the solder.
The biggest issue when you attempt to solder gold-filled products with a torch is that you can actually alloy the gold layer with the brass core. This leaves a dark, discolored solder join and any exposed brass would tarnish quicker than the surrounding metal in the piece of jewelry. This is an obvious quality problem for your customers. You want to heat your piece just to the point of solder flow between 1275-1450 degrees Fahrenheit. But, avoid overheating to the melting points of the 14 karat gold layer at 1550 degrees Fahrenheit and the brass core at roughly 1650 degrees Fahrenheit. If your gold surface layers start to melt and flow, you will have an irreversible problem.
Add a Plating Finish to Any Soldered Gold-filled Items
If either the colors don't match or the brass has been exposed, the only way to fix it at this point is to gold-plate the entire piece. This will place a layer of gold across the entire surface creating a uniform color and protecting the exposed brass from tarnishing. Since plating wears through overtime, the gold-filled jewelry piece may no longer be a lifetime product. Moreover, even if you don't notice discoloration at the solder join immediately, that point may discolor in time if the gold layer has been thinned out; so, plating to finish is always recommended on soldered gold-filled.
Note: Plating to finish a piece is always recommended on soldered gold-filled items.
Plating is an intense process that requires harsh chemicals, safe disposal, and safety training. Most jewelry studios do not have plating equipment in-house. Instead, this service is usually outsourced to a specialist job shop. There are jewelry plating companies located around the country. Usually, plating services are priced by the gram. You will need to add this additional expense into the pricing calculation for your finished item and consider the turnaround time on the plating outsourcing.
In conclusion, it may be best to avoid soldering gold-filled altogether. Consider construction alternatives in your design. Gold-filled is ideal for assembly, stamping and riveting. If you choose to solder, we encourage you to always add a plating finish for quality. Or, communicate clear expectations to your customers about discoloration issues and piece longevity.
Additional Information about Gold-Filled
Unfortunately, gold-filled items cannot be cast, so there is a limit on what findings are available. Casting requires the metals to be melted during the process, which would destroy the layered product so instead, sheet, tubing, and wire are used to manufacture gold-filled items.
Sanding and filing
You can never sand or file a gold-filled item. Sanding and filing will remove the metal and if you attempt this with a gold-filled item, you are removing the gold alloy layer. Removing that gold alloy changes the 5% total weight of your piece, so you can no longer legally call it gold-filled. Similarly, you should avoid diamond cutting, engraving or polishing with other abrasives.
Do not pierce without plating. When you pierce a gold-filled item you are exposing the jeweler's brass in the center of the hole that you have drilled. Over time that brass will tarnish and stand out. The only way to fix that exposed brass is to plate the entire piece. That solid gold plating can help keep the brass from tarnishing, however, it may not last long especially if the hole has a jump ring through it which will rub the plating down.
To remove fingerprints or grease from your gold-filled items, use a child's soft toothbrush with a mild soap. This quick polish should have it looking like new again but, you can also try ultrasonic baths and soft polishing cloths as long as the chemicals used are gold-filled friendly and the cloth is non-abrasive.
Has this article changed your opinion about gold-filled items? If so, how?
Gold-Filled 101 Video
In this video, Hilary Halstead-Scott discusses "what is gold-filled?", which includes gold alloys, gold-filled limitations, and the construction of gold-filled materials.
Additional Gold-Filled Articles:
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Questions & Answers
Q: Hi Erica, Thank you for the explanation. I bought some gold-filled ear studs recently (because I have a metal allergy, I, unfortunately, don't know against what, but gold and silver work fine). I reacted to the ear studs and when I took them out after a day, I noticed that the solder that connected the stud to the earring was discolored, now I'm wondering if that is exactly the problem described: That the inner metal was exposed there.