Characteristics of 18K gold

Caratteristiche e peculiarità dell'oro a 18 K - gioielliperfetti.it

Characteristics of 18K gold. One of the most popular gold alloys in jewelry, prized for its balance of purity, strength, and value. Here are its main characteristics and peculiarities 👇

Characteristics of 18K gold:

🧪 1. Chemical composition and metallurgical structure

THE'pure gold (24 K) It is too soft for everyday use: it scratches, bends and deforms easily.
For this reason it comes alloyed with other metals, which improve its hardness, strength and colour stability.

➤ Percentages

  • 18 K = 75% pure gold + 25% alloy metals

  • The metals used depend on the color and the desired use:

    • Copper (Cu) → increases hardness, gives warmth and red/pink color

    • Silver (Ag) → lightens the tone and increases ductility

    • Palladio (Pd) → gives white color and resistance to oxidation

    • Nickel (Ni) → once used for white gold, now avoided for allergenic reasons

    • Zinc (Zn) → improves melting fluidity

➤ Microstructure

During solidification, the gold and alloy metal atoms form a solid solution (homogeneous metallic mixture), which gives a more stable and resistant structure than pure gold.

Single Bracelet in 18K Gold with Japanese Akoya Sea Pearl

Bracciale Singolo in Oro 18K con Perla di Mare Giapponese Akoya

🌈 2. 18K Gold Colors

One of the great virtues of 18-karat gold is the chromatic versatility, which depends on the proportions of the added metals.

18K gold type Indicative composition Color Notes
Yellow Au 75% + Ag 12.5% + Cu 12.5% Intense, warm yellow Classic, traditional
White Au 75% + Pd/Ni/Zn 25% Silvery-white Often rhodium plated for brilliance
Pink Au 75% + Cu 22.5% + Ag 2.5% Rosa tenue o rosso Very fashionable
Green At 75% + Ag 25% Light yellow-green Rare, used in artistic designs

Wooden necklace with 18K gold tassels and woven rainbow lace

Collana in legno con nappe in oro 18 carati e pizzo arcobaleno intrecciato



⚙️ 3. Physical and mechanical properties

Proprietà Oro 24K Oro 18K Oro 14K
Hardness (Mohs) 2.5–3 3–4 4–5
Density (g/cm³) 19.3 ~15.5–16.5 ~13
Melting point 1064°C ~910–950°C ~880°C
Ductility Very high high Media
Corrosion resistance Excellent Great Good

👉 18K gold is therefore a balanced alloy: retains good ductility and brilliance, but with enough hardness to withstand daily use.

Handmade 18K gold cat's eye bracelet

Bracciale fatto a mano con motivo a occhio di gatto in oro 18K


💎 4. Aesthetic appearance and behavior over time

  • Brilliance: maintains a warm, rich luster, deeper than less pure alloys.

  • OxidationPure gold does not tarnish; 18K alloys may darken slightly due to secondary metals, but much less than 14K or 9K.

  • Polishability: it can be easily polished to restore its original shine.

  • Aging: tends to maintain its appearance over time, especially if stored and cleaned properly.

🧭 5. Branding and certification

In Europe and Italy, gold is mandatory branding to indicate the title (i.e. the quantity of pure gold contained in the alloy):

  • “750” → 750 parts of gold per 1000, i.e. 18 K

  • Accompanied by a goldsmith's identification mark (number and abbreviation of the province, e.g. 1234 AR (for Arezzo)

In the United States, however, the term is used “18K” or “18KT”.

⚖️ 6. Economic and usage comparison

Type % Gold Merit Common use Average price
24 K 99.9% Very tall, but too soft Ingots, coins, fine watches 💰💰💰💰
18 K 75% Perfect balance between value and resistance Luxury jewelry, rings, wedding rings 💰💰💰
14 K 58.5% More resistant, less precious Everyday jewelry 💰💰
9 K 37.5% Cheaper, harder but less shiny Bijoux, fashion jewelry 💰

🧼 7. Care and maintenance

Practical advice:

  • Avoid prolonged contact with chlorine, perfumes, acids or detergents.

  • Clean with warm water, neutral soap and a soft cloth.

  • Store separately to avoid scratches.

  • Polish periodically or rhodium-plated (for white gold).

🏛️ 8. Applications and cultural value

  • In jewelry, is the most appreciated title in Italy and in most of Europe: it represents the right compromise between luxury and functionality.

  • It is often chosen for wedding rings, high-end watches and goldsmith art objects.

  • 18K gold is also infinitely recyclable without losing quality: it can be recast and bound several times.

💬 In short

18K gold is the league of excellence of jewelry: 75% pure gold, 25% metals that increase its hardness and allow for infinite shades of color.
It unites beauty, strength, value and tradition — the perfect balance between purity and practicality.

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