Updated
HGE means heavy gold electroplate: a layer of at least 10K gold, equal to at least 2.5 microns of fine gold, plated over another metal. It is not solid gold.
HGE, H.G.E., 10K HGE, 14K HGE, 18K HGE, HGP (heavy gold plate)
Inside rings, often as 10K HGE, 14K HGE or 18K HGE, and on vintage costume jewelry.
HGE means a layer of gold over another metal, even when a karat number such as 14K sits beside it. Here is how it compares with solid gold and the other layers, shown for 14K:
| Stamp | What it means | Gold, 5 g ring |
|---|---|---|
14K | Solid 14K gold all the way through | 2.92 g $381.39 |
1/20 14K GF | Gold filled: a bonded layer of at least 10K gold, at least 1/20 of the total weight | 0.15 g $19.07 |
1/40 14K RGP | Rolled gold plate: a bonded layer, at least 1/40 of the total weight | 0.07 g $9.53 |
14K HGE | Heavy gold electroplate: at least 2.5 microns of gold | about $2.52 |
14K GEP14K GP | Gold electroplate or gold plate: at least 0.175 microns of gold | about $0.18 |
Pure gold content at today's $130.39 a gram. Plated rows assume a plain ring with about 4 square centimeters of surface at the FTC minimum thickness (16 CFR 23.3).
Gold = surface area × plating thickness × 19.32 grams per cubic centimeter
19.32 is the density of fine gold, and the HGE minimum is the equal of 2.5 microns (0.00025 cm) of it. A plain ring has about 4 square centimeters of surface: 4 × 0.00025 × 19.32 = 0.019 grams of gold, worth about $2.52.
That is the minimum. Some plating is thicker, and worn plating holds less. A solid 14K ring of 5 grams holds about $381.39 of gold.
The karat number describes only the plating. 18K and 24K HGE look a richer yellow than 10K HGE, but each is a thin layer over brass or another base metal, and at the same thickness the higher karat adds only cents of gold to a ring.
ESPO is the mark of Esposito Jewelry, a costume jewelry maker in Providence, Rhode Island, whose 18K HGE ESPO rings turn up often in vintage shops. ESPO names the maker, not the metal, so an 18K HGE ESPO ring is plated, not solid gold. As with most costume jewelry, the stones are usually glass or synthetic, and value comes from style and condition.
The 2.5 micron minimum is about 14 times the 0.175 microns required for ordinary gold electroplate, so HGE outlasts plain plating. How long depends on wear. On a ring worn every day, the palm side and edges wear through first. Pendants and earrings, which rub less, keep their color much longer. Sweat, lotion and chlorine speed up wear.
Not while the gold layer is intact. Once it wears through, a base metal such as brass or copper can react with sweat and leave a green mark on skin. Some base metals contain nickel, which can cause a rash for people with a nickel allergy. A jeweler can replate a worn ring, which restores the color but adds nothing to its value as metal.
Source: FTC Jewelry Guides, 16 CFR 23.3, gold electroplate and heavy gold electroplate.
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Heavy gold electroplate. The ring has a layer of at least 10K gold, equal to at least 2.5 microns of fine gold, over another metal. It is not solid gold.
Only the surface. 10K HGE means a 10K gold layer over another metal, so the ring is worth very little as metal.
Both are gold layers over another metal. HGE is electroplated and measured in microns. GF is a much thicker bonded layer, at least 1/20 of the weight, so it holds far more gold.
18K HGE is heavy gold electroplate in 18K gold, at least 2.5 microns thick, over a base metal. ESPO is the mark of Esposito Jewelry, a costume jewelry maker. The ring is not solid gold.
Not while the gold layer is intact. Once the plating wears through, a brass or copper base can react with sweat and leave a green mark on skin.