What '18K Gold Plated' Actually Means: Karats, Microns, PVD and the Numbers That Matter
"18K gold plated" sounds like a specification. It is half of one. It tells you the purity of the gold in the surface layer and nothing about how thick that layer is, how it was applied, or what it is sitting on — and those three things decide whether the piece looks the same in a year. Here is the vocabulary, in the order it matters.
- Karat = purity of the gold layer. 18K is 75% gold; it is the warm, classic colour.
- Microns = thickness. 0.5 is a flash; 2–3 is good fashion plating.
- PVD plating bonds harder and wears slower than standard electroplating.
- Base metal matters more than all of the above. Steel over brass, every time.
Karat: what colour the gold is
Karat measures purity out of 24. 24K is pure gold — too soft for jewellery and very yellow. 18K is 75% gold with 25% other metals, which gives the warm but not orange colour most people picture as "gold". 14K is 58% gold and slightly paler. In plating, the karat tells you the colour of the layer and very little else; an 18K layer half a micron thick will wear through faster than a 14K layer three microns thick.
Microns: how thick the gold is
A micron is a thousandth of a millimetre. Plating thickness in fashion jewellery runs from about 0.1 microns (a "flash", which is a colour wash that wears in weeks) to 2.5–3 microns for good daily-wear pieces. Gold vermeil is legally defined in some countries as at least 2.5 microns over sterling silver. Most listings don't state thickness; brands that plate thickly tend to say so, because it costs more.
Electroplating vs PVD
Electroplating uses an electric current to deposit gold from a solution onto the piece. It is the standard method, gives an even finish, and its durability depends on thickness and on the underlayer.
PVD (physical vapour deposition) vaporises the metal in a vacuum chamber and bonds it to the surface at the molecular level. The result is harder, more scratch-resistant and more evenly bonded than electroplating at the same thickness. It works particularly well on stainless steel, which is why PVD-plated steel has become the standard for watches and for daily-wear jewellery. ENSIA's hoops and cuffs are PVD-plated for this reason; where a piece is electroplated, it is plated thickly and sealed with an anti-tarnish coat.
The base metal, again
Every guide we write comes back to this because it is the variable that matters most. The gold layer is microns thick and will eventually wear at contact points whatever the method. What shows through then is the base. On brass, that is a dark or green patch. On stainless steel, it is silver-grey metal that doesn't react. Our steel vs brass comparison has the detail.
The other terms you will see
- Gold-tone / gold-coloured: no gold at all. A lacquer or a brass finish.
- Gold vermeil: gold plated over sterling silver, minimum thickness. Good, but silver tarnishes and needs polishing.
- Gold filled: a thick gold layer bonded under heat and pressure, typically 5% of the piece's weight. Durable, expensive, rare in India.
- Anti-tarnish coat: a clear seal over the gold. Explained in our anti-tarnish guide.
- Hypoallergenic / nickel-free: about the base metal's effect on skin, not about the gold.
Questions worth asking a brand
- What is the base metal?
- How is it plated — electroplated or PVD — and roughly how thick?
- Is there a coat over the gold?
- What happens if it fades — is there a time-bound guarantee?
A brand that can answer all four is selling jewellery. A brand that answers with "18K gold plated, anti-tarnish, hypoallergenic" and nothing else is selling a keyword. ENSIA's answers: 316L stainless steel; PVD or thick electroplating; yes, anti-tarnish coat; and a 6-month replacement promise on the finish.
