Bronze watches are more prevalent now than they've ever been, to a point that I'd argue that there's more bronze than platinum available in the watch market at present day. The appeal is simple. To some, it's nothing more than a colorful alternative to steel, titanium, or DLC. To others, it's the idea of a watch that's constantly evolving, whose character is designed to change over time. Beyond that, there's the 'sciencing appeal' (no, sciencing isn't a word, but you get where I'm going with it). Having the ability the ability to force patination of the metal through different means is what draws some to collect bronze watches, myself included. Through this process, this experimentation, this 'oops I went too far now how do I bring it back' adventure I've been on, I've learned a great deal about the variations of the alloy-how they react, and their individual quirks.

With this experience in mind, the thoughts behind this series is really about sharing the life lessons that have come out of an ever-changing bronze watch collection. If you're contemplating adding a bronze watch or three to the collection, there are plenty of things to consider, so with each instalment of this series we will be covering different bases, covering everything from more general information, to lessons in cleaning, forced patina, and the risks involved in any sort of watch tampering. For today, let's kick things off with 'the basics'.

Not All Bronze Is Created Equal

Even by just taking a quick look at the different bronze watches on offer today, you'll quickly realize that bronze is by no means as consistent as steel or gold. On one end of the spectrum, watches like the Tudor Black Bay Bronze, the Halios Seaforth B , the Yema Superman , and last year's IWC Spitfire Chronograph in bronze have a distinctly yellowish hue that adopts a more muted grey coloring as it ages. Oppositely, bronze offerings from Oris , Zelos , Meistersinger , and others are much more warm and rosy.

The differences, as you'd expect, come down to chemistry and composition. Bronze is an alloy, primarily made up of copper, but what fills the rest of the alloy can vary substantially all while still falling under the umbrella nomenclature of bronze. Bronze can be called such so long as it's composed primarily of Copper and has at least a small portion of tin (and other metals), but as metallurgy has evolved, what makes up the balance of the composition has varied. Based on available information, typically two basic variations of bronze are used in watchmaking.

It remains a bit of a frustration that many brands don't disclose which bronze type they've chosen when they post spec sheets. Once you're more familiar with the material it's not rocket science to detect, but to those less familiar, a little information could come in handy. After all, if you've been enamored with the Black Bay Bronze, and ended up buying an Oris Carl Brashear, the end results of your patina journey are going to be painfully different after months/years of wear. This all might seem a bit basic to some of you, but before we dig into the experience of living with bronze, we want to make sure that everyone is equipped with some good baseline knowledge.

Aluminum Bronze

Aluminum bronze watches make up the first half of our examples in the paragraph above-those yellowy grey cases that patina in a more understated manner. Aluminum bronze is frequently used in marine applications, and is generally more corrosion resistant. This also means that it is slower to patina, as I've learned with both the Halios Seaforth and Yema Supermarine. The addition of between 9 and 12% aluminum, and 6% iron and nickel means less copper in the alloy, which is what leads to the cooler and more yellow hue of these cases. By and large, these pieces are better suited to those wanting to let their watch age naturally, and we've seen some great examples in our forums and elsewhere across the web.

CuSn/Phosphor Bronze

Though there is still some variance in CuSn Bronze, the basics are simple. They're copper-heavy, with the balance of elements being comprised of Tin, Phosphorus, and other elements. Tin can range between around 6 to 8% (often seen as CuSn6 or CuSn8), whereas Phosphorus is less than 1% of composition. you'll still get some color variation in these cases from one to the next, but generally speaking it's easy to single them out in comparison to Aluminum Bronze. By comparison, these cases take quite well to forced patina, regardless of method, but the results can vary dramatically from case to case. You'll see more warmth come out in its color as it darkens, and occasionally even some peculiar textures will begin to appear in the metal.

Frequently Asked Questions

Between myself and about a dozen other patina geeks, I've compiled some basic questions that are most often thrown around to those who have been dabbling in bronze watch collecting through the last half decade or so.

Is Patina Reversible?

The best way to answer this question is by saying yes, but. We'll cover an entire instalment on the cleaning process at a later date to clarify this further, but at a basic level you can remove patina from a bronze watch case. Where the 'but' becomes applicable is when it comes to case finishing. Depending on how heavy the patina is, surface treatment and soft cloths won't necessarily cut it, and if you're talking about a polished case, turning back fully isn't really an option. That said, sometimes the aesthetics of the reversal can be really interesting. My Zodiac Super Sea Wolf 68 Bronze has gone to the dark side and back on several occasions, and at present its color is close to original, with an interesting texture to it that wasn't initially apparent in its original microblasted finish.

Can Forcing Patina Damage My Watch?

This is another loaded question, and the unfortunate answer is yes, sometimes it can. As a rule of thumb, I would never force patina on something without a screw-down crown, and even with a screw down crown, it is possible to go overboard. Just recently (on a watch that shall remain nameless) I subjected a piece to repeated long sessions of vinegar fuming which included temperature shifting as well (placing the sealed container with watch/fumes into a hot water bath to create vapor condensation). After several weeks of this, with intermittent pauses to rinse off the case, condensation was detected under the watch crystal. As it stands the watch is with my watchmaker to uncover which gasket failed and how, but this is exactly the kind of risk we run with these experiments.

That said, having patina naturally occur on bronze usually does not, and will not cause damage to a watch (case or otherwise). Patina on bronze is surface oxidization, and it (at a basic level) is creating an outer layer on the surface on the metal rather than eating away. It's not the equivalent of a rusting body panel on a car. Even when at the point of this greenish dust forming, this is still a matter of the surface of the material rather than something to panic about. If you let your watch age gracefully, you shan't be worried. If you get overzealous as I did, you might have to spend a couple hundred bucks with your watchmaker to fix your own foolishness.

There is one last note to be made here that especially applies to the affordables space. We have seen some cases where the specific bronze alloys used some manufacturers (Makara and Maranez have been culpable of this) is a bit more prone to corrosion, and some owners have seen pitting occur in the metal itself. It's rare, but it has happened.

How Long Does Patina Take?

This is a question that is immensely variable depending on everything from how much you wear your watch, to what climate you live in, to the type of bronze used on the case. Phosphor bronze does age quicker, without a doubt, with some pieces starting to show signs of aging within the first couple of days of wear. Aluminum bronze on the other hand can take weeks to start to shift, and is much more subtle as noted above. As a point of reference, have a look at the images below.

The Halios Seaforth and Zelos Swordfish were both acquired at the end of October, 2019. The second image was taken on June 24th 2020. They've seen close to the same amount of wear in the same environment, but the aluminum bronze of the Halios has been taking its sweet time to age (both naturally.