Gold plating is a common thing we all have to deal with in the jewelry business. Often, we run into some terminologies or measurement units that sound similar and it can get confusing. Below we go through some basics in gold plating to help you understand the process further.
Gold Plating Measurement
Before we dig into the gold plating details, let’s review some basic measurements of gold plating.
Microns vs. Millionths
You will hear most of the jewelry vendors and manufacturers talk gold plating thickness in microns. But, when you speak to plating company technicians, you may hear them use millionths. What is the difference and how do you convert them?
Micron is a unit of measurement in the metric system. It is one-thousandth of a millimeter.
Millionths normally refer to Millionths of an inch. It is a unit of the Imperial system and equals a millionth of an inch.
To convert them, use this formula:
1 micron = 40 millionths of an inch
Commercial Plating vs. Guaranteed Plating
When you talk to the manufacturer about the thickness of the gold plating please be aware that there are more than just the number and measurement units to discuss. When they tell you a piece of jewelry is 0.5micron gold plating, you need to ask if that is commercial plating thickness or guaranteed plating thickness as there is a difference. So what is the difference between the two?
Basically, commercial plating thickness is just a rough target thickness number they try to meet. A claimed 0.5 microns plating may be just about 0.3 to 0.35 micron thickness on average. The plating equipment is not set up to plate the gold layer at a very accurate thickness. They try to make it close to the declared thickness, but normally it’s less than that for the obvious reason. This is normally a very cost-effective way to do the plating if the thickness accuracy is not a big deal.
Guaranteed plating is plating at a much accurate level. Most of the specialty plating firms and bigger jewelry manufacturers can do guaranteed plating. Their equipment is more advanced and can do plating at a more accurate level. For guaranteed plating, they will test thickness, normally by an x-ray fluorescence test to make sure the results meet the declared thickness. That’s why guaranteed plating is a lot more expensive than commercial plating for the same thickness.
The Thickness of Gold Plating
Most of the gold plating is done by a process called electroplating. The jewelry piece will be in a gold liquid and a thin layer of gold will be deposited on it by applying a direct electric current. This process will partially dissolve the gold and create a chemical bond between the jewelry pieces and the gold to form a gold layer on the top.
The jewelry industry uses different names for each plating thickness range:
- Flash Plating or Gold Wash
Flash plating is electroplating of gold at the thickness no more than 0.175 microns or 7 millionths of an inch. It basically just dips the jewelry piece into the gold liquid and gives it a gold finish.
- Gold Electroplate
Electroplating of gold at least 0.175 micron or 7 millionths of an inch, but no more than 0.5 micron or 20 millionths of an inch. This kind of plating can be marked as “G.E.P.”
- Gold Plate
If you advertise your jewelry as “gold plated” it legally needs to have a minimum gold layer thickness of 0.5 microns or 20 millionths of an inch.
- Gold Vermeil
This is heavy gold plated over a solid sterling silver piece. The thickness of the gold layer needs to be at least 2.5 micron or 100 millionths of an inch. There is normally a very thin barrier layer, like palladium, between gold and silver as well.
Unlike several decades ago, most vendors currently do not supply real Vermeil jewelry because of the high price of gold and the easier market access to new alternative materials, like gold-filled. 2.5 microns gold plated jewelry can be very expensive compared to the same piece in just sterling silver. Vendors and manufacturers often choose from 0.1 to 1 micron gold plating to keep the cost reasonable. Most of the sterling silver jewelry with gold plating on the top are advertised as “Gold plated sterling silver”, “Gold over Sterling Silver”, or “Vermeil Style”.
Because the price of gold keeps increasing, manufacturers keep finding better ways to lower the thickness of the gold layer and still have a jewelry piece that can last. Therefore, a coating layer is needed, especially for the thin plated jewelry, to help maintain the gold layer.
- E-coating (Lacquer)
It can be easy to confuse the terms electroplating and e-coating, but they are totally different processes. Electroplating is the process we use to deposit gold on top of other metals. E-coating is a process that coats the gold layer with lacquer like material to protect the gold layer from wearing off or tarnishing. It is a very efficient and cost-effective way to protect thin gold plating jewelry pieces.
- Nano Polymer Coating
Nano polymer is a new technology that results in an invisible protective layer on a jewelry piece that is skin-friendly and hypoallergenic. It can also protect silver jewelry from tarnishing without affecting its natural silver color as rhodium plating can do. It can also protect gold plating or other metallic surfaces.
Now with all this information, it comes to the question of how you can test or confirm a piece of jewelry is plated at a declared gold thickness? The gold plating thickness can be tested by x-ray fluorescence (XRF) testing. A simple non-destructive test will cost from $20 to $30. Many specialty plating firms or testing labs can do it and provide you a test report at the end. You can google “XRF testing service” in your area to see who offers gold plating thickness tests.
I hope this article gives you basic knowledge about gold plating and its terminologies. Please feel free to discuss this in more detail in the comments below.