Why CuSn8 Bronze
CuSn8 bronze is always considered the premium choice and industry “gold” standard when it comes to bronze watches, despite being considerably more expensive than alternatives such as aluminum bronze or even brass, that one can often find in lower spec'd and less desirable timepieces. This is for two important reasons:
- It's a corrosion resistant† marine grade alloy, perfect for a bronze dive watch!
- Bronze watches are all about the unique patinas that can develop over time, an oxidization layer that can help protect the watch as well as give each watch a subtle unique “aged” look as it changes color. CuSn8 bronze is particularly admired for it's ability to develop a rich deep brown patina compared to say aluminum bronze, which tends towards a less desirable lighter reddish brown.
Little wonder then that CuSn8 bronze has been the go-to choice for many famous luxury brands such as Bremont, Panerai, and IWC, to name just a few.
Customizing Your Patina
When newly manufactured, CuSn8 bronze has a warm gold-like color, a shiny golden brown which looks awesome, and is easily distinguishable from the greener hues in some other alloys. As it is exposed to the air, (or water,) it will start to develop a patina. Spotting is possible in new watches where parts of the watch have started to patina but other areas may still be more gold-like. Given time, the entire case will develop a more consistent patina that can give rise to some wonderful looks. However, sometimes you don't want to wait months to fully develop your patina, so we have one suggestion that can shorten things to a matter of minutes or hours instead:
Taking the egg yolk from a hard-boiled egg and placing it in an airtight container with your CuSn8 watch head can introduce a rich brown patina, which has the added bonus of being a protective oxidization. Care should be taken to avoid contact with the egg, and we would recommend having the watch raised on the sapphire crystal and steel exhibition case back so all bronze areas of the watch have a uniform exposure. Keep a close eye on the watch and remove and rinse under cold tap water open once you get the desired color. Then you can burnish or lightly polish it with just a microfiber cloth, which will help slow down any further changes.
Other colors are possible, and there are plenty of YouTube videos that detail the use of different household products such as vinegar. However we do recommend researching those carefully first as some combinations can introduce a corrosive green finish.
Resetting Your Patina
If you don't like the color or really love the golden look and want to remove any spotting, you can soak the watch head in lemon juice. This is the method with the least amount of work, but one you should avoid if the watch is not new as the dive seals may have aged and need replacing.
Two alternatives are: use a cheap [abrasive] toothpaste and toothbrush with a little water, which is good for removing light spotting but difficult for anything more, or use a Cape Cod Cloth, which is highly recommended and the process we follow in-house.
Maintaining Bronze Watches
When swimming with your watch, if you are in a pool with chlorinated or chemically treated water then we strongly recommend rinsing the watch in cold tap water afterwards to wash off any chemicals. We also recommend a quick rinse after salt water bathing or after excessive sweating too.
As with all dive watches, don't forget to always keep the crown fully screwed around water. Always keep the crown screwed down except when winding or adjusting.
It's also always worth mentioning that no watch should ever be introduced to a sauna, steam room, or hot water, such as a hot bath, hot spring, or hot tub. This includes all dive watches and is because the air inside the watch case can condense into water droplets that will most likely severely damage the mechanical movement fairly quickly. If your movement has been exposed to moisture, it should immediately be serviced.
† CuSn8 bronze is more corrosion resistant than most other bronze or brass alloys, but like other metals, can corrode when exposed to some chemicals.
