Section 10: The Materials Used in Watchmaking

The history of watchmaking spans several centuries, and the materials used in its craft have evolved continuously. The quality of those materials has improved steadily, and new materials are constantly emerging — each finding its place in the production and manufacture of timepieces.

The range of materials used in watchmaking is vast, their properties diverse, and their surface finishing techniques highly specialized. This section provides a concise introduction to the fundamental knowledge of watch materials and their associated processes.

The materials used in watchmaking fall into two broad categories: metallic materials and non-metallic materials.

At Aorawa Time, every timepiece in our collection is chosen with materials and finishing in mind — because what a watch is made of is inseparable from what it is worth.

I. Metallic Materials

The two most important metals in watchmaking are copper and steel.

1. Copper

Copper is one of the primary materials used in watchmaking. An alloy of copper, aluminum, and a small amount of lead is known as leaded brass. Components such as plates, wheels, and dials are typically made from brass.

2. Steel

Free-cutting steel is one of the primary materials used in watchmaking. Gear shafts, pallet levers, and miscellaneous components within the movement are all manufactured from free-cutting steel.

3. Stainless Steel

Stainless steel — also known as jinggang (精钢) in Chinese — is the dominant material for watch cases, casebacks, and bracelets.

(1) Adding 12% chromium to steel gives it corrosion resistance in air, water, acids, alkalis, and salts. Steel with less than 12% chromium is prone to rust. This type of steel is magnetic and is not suitable for watch cases.

(2) Another category of stainless steel contains both chromium and a large amount of nickel, known as nickel-chromium stainless steel. This material is non-magnetic, has high tensile strength, excellent ductility, and strong corrosion resistance — making it the ideal material for watch cases and bracelets. Cases and bracelets typically use 0Cr18Ni9; casebacks use 1Cr18Ni9Ti.

Note: Titanium-free stainless steel has better corrosion resistance but inferior polishing performance.

(3) The European designation is 316L, now produced according to the American ASTM standard (equivalent to China's 0Cr17Ni12Mo2).

316L stainless steel offers excellent corrosion and wear resistance. Its surface does not require electroplating — polishing, sandblasting, or brushing alone creates a variety of three-dimensional visual effects. For these reasons, cases and bracelets are predominantly made from stainless steel, and most watch manufacturers use 316L.

(4) Rolex uses 904L stainless steel (00Cr20Ni25Mo4.5Cu). 904L is harder and more corrosion-resistant than 316L, with a price approximately three times higher. Apart from Rolex, virtually no other manufacturer uses it.

4. Precious Metals

Gold, silver, platinum, and other precious metals are rare in the earth's crust and costly to extract, which is why they command high prices. These metals are dense, have high melting points, are chemically stable, and resist acids and alkalis. Gold, silver, palladium, and platinum are all highly malleable and are widely used in the jewelry and watchmaking industries.

(1) Gold (Gold Alloys)

• Cases and bracelets of high-end watches are predominantly made from gold.
• Pure gold is too soft — its hardness and strength are insufficient for practical use — so gold alloys are used in manufacturing. 24K is 100% pure gold; 18K contains 75% gold and is the most widely used. 14K and 10K have higher hardness and strength and are preferred by consumers in the Americas. In Asia, particularly China, 18K gold is more popular — anything below 18K is perceived as insufficiently prestigious.
• K gold is further divided into yellow gold, red gold, rose gold, and more.
• White gold is a specially formulated K gold with a pale color, electroplated with a layer of rhodium or iridium, giving it an appearance similar to platinum. Important: white gold must not be polished (unless re-electroplated after polishing).

18K gold alloy compositions:

• 18K Yellow Gold: 75% gold + 16% silver + 9% copper
• 18K White Gold: 75% gold + 3% silver + 9.5% copper + 12.5% palladium
• 18K Pink Gold: 75% gold + 12.5% silver + 12.5% copper
• 18K Rose Gold: 75% gold + 9% silver + 16% copper
• 18K Red Gold: 75% gold + 5.5% silver + 19.5% copper
• Three-color gold: 18K White Gold + 18K Yellow Gold + 18K Rose Gold

Other K gold grades include 9K, 10K, 12K, and 14K. For example, 14K yellow gold is 58.5% pure gold + 26.5% silver + 15% copper.

(2) Silver and Platinum Group Elements

• Silver: Silver cases were common in early pocket watches but are rarely seen today. Silver oxidizes easily — once oxidized, the surface darkens. Polishing or soaking in "silver cleaning solution" removes the oxidation layer and restores its luster.
• Platinum (Pt): The highest-quality precious metal of all. Platinum is expensive; purity is expressed as Pt950, Pt900, etc.
• Platinum group elements: Expensive and generally used for surface electroplating, including ruthenium, rhodium, palladium, osmium, iridium, and rhenium.

Note: Please refer to Section 18 of this chapter for precious metal hallmark information.

5. Titanium and Titanium Alloys

(1) Titanium Metal

Pure titanium has a silver-white color and belongs to the category of lightweight metals. Titanium is chemically very reactive — it readily interacts with oxygen, nitrogen, and hydrogen in the air, forming an extremely stable compound on its surface. The titanium we commonly encounter therefore appears grayish-black. Its melting point is (1668 ± 10)°C and its density is 4.5 g/cm³.

The key characteristics of titanium are: high strength, light weight, corrosion resistance, good low-temperature performance, and additional special properties including superconductivity, shape memory, and hydrogen storage. Its relative density is approximately 50% that of stainless steel, yet its strength is comparable.

In practice, pure titanium is rarely used. What is commonly referred to as "titanium" in the watch industry generally means titanium alloy.

Titanium alloy is a new material that began development in the late 1940s, entered a research and development phase in the 1950s, became an industrial-scale material in the 1960s–70s, and entered widespread application in the 1980s–90s. Since 2005, an increasing number of watch brands have adopted titanium — including Sinn, Hublot, Khaki, Tianji, and Bvlgari, among others.

Titanium alloy is composed of titanium combined with aluminum, vanadium, nickel, molybdenum, and other elements.

(2) Tungsten-Titanium Alloy

Tungsten carbide and titanium carbide powders are first pressed into blanks under 1,000 Pa of pressure, then die-cast, and finally sintered at 1,450°C in a specialized furnace to produce extremely dense components. After multiple finishing processes using diamond powder, the result is a brilliantly lustrous tungsten-titanium alloy with excellent wear resistance.

Swiss Rado was among the first to use tungsten-titanium alloy for cases and bracelets in the 1970s–80s, earning strong consumer acclaim.

6. Cemented Carbide (Tungsten Steel)

Cemented carbide — also known as tungsten steel — has high hardness, excellent wear resistance, and sharp, clean exterior lines with a bright finish. It is known as a "wear-resistant material" and can be used in combination with steel to create case bezels, bracelets, and bracelet links, enhancing the corrosion resistance and decorative appeal of the case and bracelet surfaces.

The material a watch is made from is not merely a technical specification — it is a statement of intent. Explore timepieces crafted from the finest materials at Aorawa Time.