There are unusual materials used in watchmaking today that stray from the traditional. Wood, carbon fiber, recycled plastics and sapphire crystal are a few, but the majority of cases and bracelets stick with tried and true metals. Stainless steel is the most common and found in both affordable and high-end watches, and everything in-between. Precious metals like gold and platinum are generally reserved for the luxury space, although silver, titanium and even aluminum are also seen here. Sometimes a material is used solely for status, such as gold, while other times it serves a very functional purpose (like titanium or stainless steel). Let's take a look at some of the most common metals used for watch cases and bracelets.
Stainless Steel
Stainless steel has grades like gold (and other metals) and the most common type in watchmaking is 316L. It's durable, highly corrosion resistant and anti-magnetic. There’s a lower grade called 304, which is the most common type for general use. Utensils, pans, appliances, etc. are most likely 304 as it’s cheap, easy to work with and widely available. In watchmaking, 304 is reserved for lower-end brands as corrosion resistance is inferior. Specifically, sweat and salt water don’t play well with 304 over time, something watches are inevitably exposed to.
Stainless steel differentiates itself from regular steel with additional metals like chromium (at least 10.5%). This metallic element provides a desirable sheen, especially when polished, and the presence of other metals also greatly reduces magnetic properties as the alloy strays from its steel base. 316L goes by a few nicknames like “surgical steel” or “marine-grade steel” as it dominates those applications due to superior corrosion resistance and overall durability. The “L” in 316L has meaning as well. There’s a 316 grade of stainless steel (no L) that has higher carbon and molybdenum content, which makes it less desirable for watches as it’s a bit more vulnerable to magnetism and corrosion. 316L can’t exceed 0.035% carbon content (compared to 0.08% for 316). Confused yet? Well, there's an even better variant called 904L, which is a favorite of Rolex (known as Oystersteel) and used in the majority of Horage's steel watches.
904L Stainless Steel
Horage chooses 904L stainless steel as both corrosion resistance and the aesthetics are superior to 316L, especially for dive and sports watches exposed to seawater and sweat. From a technical standpoint, 904L has more carbon (0.2% max compared to 0.035% max for 316L), up to 5% more chromium, an addition of copper and around double the amount of nickel. The main takeaways here are the increase of both chromium and nickel (and slight increase of molybdenum), and introduction of copper. They increase corrosion resistance even more, particularly with acids, and provide a superior sheen when polished thanks to increased chromium. Some marketing materials even compare 904L to precious metals as the outstanding corrosion resistance and polishing characteristics are comparable to gold. 904L also has an almost total resistance to magnetism.
Titanium
Few materials continue to have an exotic appeal long after becoming mainstream and titanium arguably reigns supreme in this category (outside of precious metals like gold or platinum). It provides a rugged metal look and feel, but in a very light and premium package. It’s not the super rare and expensive metal that it once was, but its continued allure in watchmaking and beyond is unmistakable. Many believe that Porsche Design offered the first titanium watch in 1980, but it was actually Citizen that introduced the first titanium case a decade earlier, the X-8 Chronometer. It was a big deal at the time as titanium was rare, very hard to work with and a superstar for top secret aircraft like Lockheed's SR-71 Blackbird in the 1960s. Believe it or not, titanium was actually discovered back in 1791, but it wasn’t until the early 20th century that the metal was processed to a level where it was genuinely useful (over 99% pure without being brittle).
Following World War II, the perfected manufacturing of titanium meant it was twice as strong as aluminum, 40% to 45% lighter than stainless steel (but just as strong), incredibly corrosion resistant with a very high melting point. This makes it perfect for high-speed aircraft, spacecraft and sea water applications, but it's also great for watches. With watch cases commonly measuring over 40mm in diameter, they’re heavy when coupled with steel bracelets. Titanium significantly reduces the weight while also being so hypoallergenic that it’s classed as biocompatible. This means it can be implanted in the body without negative reactions or rejection (dental implants, pins for broken bones, etc.).
Horage has embraced titanium for the new Lensman 1 and previous Autark collection, including the Autark 10-Years that celebrated the 10th anniversary of our K1 automatic. Titanium can be prone to scratches, so we utilized a blast hardened variant with a hardness value of 1,100 Hv (7.5 times harder than steel). A smooth matte finish provides a stealthy aesthetic that’s anti-reflective with an aerospace vibe, while the Autark T5 has a brilliant polished finish combined with matte surfaces. Grade 5 titanium is used as it’s both strong and practical to machine. It’s alloyed with 6% aluminum and 4% vanadium (Ti 6Al-4V), but specialized tools are required for milling. Due to high tensile strength and other factors, titanium is among the most difficult of metals to work with, which contributes to its higher cost. Benefits outweigh the hardships, of course, and Horage watches have only benefited from this titanium armor.
Gold
Gold comes in many varieties, from color to purity, and is arguably the most desirable of precious metals. Notwithstanding white gold, the metal is instantly recognizable and always associated with opulence. Have you seen the inside of Tutankhamun’s tomb? The most common grades are 14k and 18k, while 24k is pure gold. Unfortunately, 24k gold is too soft for most applications, so other metals must be mixed to create a gold alloy. A quick note about measurements – a carat is used to weigh diamonds and other gemstones, while a karat refers to the purity of gold. 18k is most preferable for high-end watches and jewelry as it’s about as pure as it gets (75% gold) without compromising durability. It’s the grade we’ll refer to from here on. Colors include red (about 25% copper), rose (about 2.5% silver and 22.5% copper), pink (about 5% silver and 20% copper) and 3N yellow (12.5% copper and 12.5% silver). White gold is silver in color like platinum or stainless steel, and contains 75% gold and 25% nickel, palladium, silver and/or other metals. Most white gold is also plated with rhodium to give it a polished silver shine as it would be a bit dull without it. Horage hasn't used gold often as our focus tends to be on movement engineering, quality and overall value, but it was an option for our first tourbillon piece, the Tourbillon 1.
Platinum
Platinum is generally more prestigious than gold as it’s a rarer precious metal. Silver in color and a noble metal like gold (very corrosion resistant), it’s used in watch cases and bracelets for very high-end pieces. It’s also heavier and stronger than gold, so most alloys are 90% to 95% pure (contributing to the additional expense). Platinum has uses in watchmaking beyond cases and bracelets, such as the material for micro-rotors. Its density and weight make it perfect for the smaller, offset rotating mass as it’s more difficult to wind the mainspring than lighter central counterparts. Gold is also used for this (and tungsten), but stainless steel micro-rotor watches occasionally use platinum rotors for both efficiency and a little bling factor. After all, it’s cooler to have some platinum in your high-end watch than tungsten, although our tungsten micro-rotors are gold-plated. Platinum is also used in catalytic converters (between $100 and $300 worth) as it’s resistant to high temperatures and oxidizes carbon monoxide and hydrocarbons. Supersede has the option for an upgraded PT950 platinum micro-rotor in the K2 movement for a bit of extra prestige.
Bronze
Bronze has been exploding in the industry as of late and just about every brand seems to have at least one or two models in this durable metal. It has a similar warmth as gold at a fraction of the price, but does form a patina over time. Gold resists corrosion and with very few exceptions, will always maintain its color and brilliance. It was first used around 3500 BC by the ancient Sumerians and is generally an alloy of copper and tin (88% copper and 12% tin), but many variants exist with added zinc, aluminum, silicon and more for a desirable look or application. In 1988, Gerald Genta’s Gefica was among the first luxury watch cases to use bronze, but it was Panerai that really popularized its use in watches. In fact, it was using bronze as early as 1985 with four prototypes (another four were titanium). Panerai's Luminor Submersible 1950 3 Days Automatic Bronzo (ref. PAM382) is credited with starting the bronze craze in watchmaking in 2011. It perfectly fit the brand as it specialized in professional dive watches and bronze was historically used in old diving equipment. The watch was an instant hit and many bronze Panerai models followed, and the majority of brands soon jumped on the bronze wagon.
Everything Else
There are other metals used in watchmaking like aluminum, silver and brass, but those are less common than the ones mentioned above. We feel that 904L stainless steel and Grade 5 titanium are optimal materials for the majority of our portfolio as they're durable, highly corrosion resistant and very aesthetically appealing. Precious metals like gold and platinum are also very desirable, but as performance watchmakers, we want to offer the best engineering and designs without additional markups for metals that add little or nothing to quality, durability and the feel of a watch. We've made a few exceptions, but those have always been optional upgrades like our 18k gold Tourbillon 1 case and platinum K2 micro-rotor.
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Erik Slaven