Much has already been said about Cartier’s excellent Santos collection, that was refreshed in 2018 with a new case design, tool-free link removal and bracelet swap mechanisms, and an in-house manufactured mechanical movement. As a watch that first debuted as a piece-unique for aviation pioneer Alberto Santos-Dumont back in 1904, the Santos is richer in history than any other timepiece currently in production, and it certainly doesn’t want for journalistic coverage as a result.

Rather than re-tread old ground, this article is focused on technical nuances of the Santos that haven’t been widely written about before, either via Cartier’s official press releases or the major Internet blogs. As someone keenly interested in the Santos personally, I’ve been (very politely, but very persistently) annoying Cartier’s press department for the past several years for answers to some nitty-gritty technical details that were important to me. Here are some of the questions that I’ve asked, and some rather surprising answers that have come back from their watchmaking department.

Santos Large in ADLC coated steel, ref WSSA0039. Image: © Cartier

How resistant to magnetism is the Cartier Santos?

It might come as a surprise to some of you that the Santos is strongly anti-magnetic. That fact isn’t advertised anywhere on the official product page on Cartier’s website, and was only revealed to the public via some investigative journalism from Hodinkee in their Week on the Wrist Review of the Santos in 2018. The author Stephen Pulvirent wrote:

The caliber also makes use of nickel phosphorous components that make it extra resistant to magnetism, plus it’s covered with a paramagnetic alloy inside the case. Cartier doesn’t provide an exact Gauss measurement, but does say that the Santos is “effectively resistant to the powerful magnetic fields a watch may be exposed to in everyday life.”

Naturally, being the details-obsessed watch fanatic that I am, I wanted more specifics on exactly how resistant to magnetism the combination of a nickel-phosphorous escapement and a paramagnetic shield would make the Santos. After querying Cartier’s watchmaking department, I received the following answer:

“The watch is resisting to 1200 Gauss”

This response really surprised me. 1,200 Gauss is equivalent to about 96,000A/m, or amperes per meter. The ISO 764 standard for an anti-magnetic watch is 4,800A/m, aka 60 Gauss, making the Santos 20x more resistant to magnetism than the ISO standard requires. That is enough to resist a chance encounter with even the strongest permanent magnets found within the likes of floor-standing loudspeakers or messenger bag clasps. Why Cartier doesn’t advertise this about the Santos is anyone’s guess, but it is a big selling point for a daily wear watch to not have to worry about magnetism at all.

Santos Large in Steel, ref WSSA0018. Image: © Cartier

Does the caliber 1847 MC within the Santos use a uni-directional winding rotor, or a bi-directional?

This can be important for the desk divers amongst us that are perhaps a little less physically active than we should be. A uni-directional rotor, as the name suggests, winds the mainspring in only one direction, while a bi-directional rotor uses reverser wheels to wind the mainspring in both directions. The latter is more desirable for ensuring the watch remains wound even for the more sedentary prospective owners. Cartier’s answer:

 “Yes, the automatic rewinding is bi-directional”

As someone who has been guilty of letting his watch run down during some low-key couchbound weekends, this was good to know!

Santos case flank showing the blue cabochon spinel set into the crown. Image: © Cartier

Is Cartier’s steel ethically sourced?

Cartier is known as an ethical jeweller, being a founding member of the Responsible Jewellery Council as well as providing extensive support to charities and NGOs via Cartier Philanthropy. While periodic audits from the RJC ensure that Cartier’s chain of supply for precious metals and gemstones is conflict-free and sustainable, nothing is mentioned about where and how they source their base materials, like steel. Cartier’s answer:

“Our steel is compliable with the REACH regulation”

This is a complex answer to unpack. REACH is a set of European Union regulations which aims to “improve the protection of human health and the environment from the risks that can be posed by chemicals”. Watchuseek forum member @Nathan356 provided some clarification on what REACH compliance means with relation to steel in watchmaking:

“it covers environmental, health and safety in a wide variety of industries. So, as an example in the steel industry, it would look at the kinds of chemicals that might be used in the manufacturing process of the steel, banning certain kinds of chemicals and other pollutants that might be hazardous to the environment or to the health of employees. This can be pretty wide-reaching (no pun intended…) because there are a lot of chemicals used in the lubrication, corrosion prevention, cleaning, and other upkeep of machinery needed to manufacture and process steel itself that would be examined for their hazardous properties and would need to be phased out and substituted. To my knowledge it doesn’t regulate the source of the actual ore.”

It is reassuring to know that even for base metals like steel, Cartier are taking steps to ensure their manufacturing is as least-hazardous to the environment and human health as possible.

“QuickSwitch” system allowing for tool-free changing between the bracelet and strap. Image: © Cartier

What specific kind of steel does Cartier use for the Santos? Is it the industry-standard 316L, or a different alloy?

This might seem obvious – everyone uses 316L except for Rolex, why wouldn’t Cartier? – but the answer surprised me yet again. Cartier’s response:

“In the majority of our watchmaking pieces we do use the standard 316L. For the gold & steel versions we use a more high end steel”

A more “high-end” steel, you say? Interesting! To the further irritation of Cartier’s much-beleaguered press department, I asked them for clarification on what kind of steel the two-tone models use. This answer took a LONG TIME to procure, and I strongly suspect there’s a picture of me somewhere at Cartier HQ for throwing darts at by now. But the response, when it finally came, was well worth the wait:

“All-steel models use regular 316L (EN 1.4435), while the two-tone steel and gold versions use 316LVM (EN 1.4441 “implant grade” stainless steel)”

Here’s a description from a Swiss metals supplier on 316LVM:

“Austenitic stainless steel with similar composition as 316 L, but with restricted tolerance for impurities. This stainless steel presents a greater corrosion resistance as compared to 316 L and is particularly adapted for medical applications (e.g. Implants). This steel complies with the standard EN 1811 and can be used for products in direct and prolonged contact with skin.”

Chemically, the biggest changes between 316L and 316LVM are the higher nickel and molybdenum content in the latter (Ni 10% in 316L Vs 14% in 316LVM, and Mo 2.1% in 316L Vs 2.8% in 316LVM), granting the “implant grade” version greatly improved resistance to pitting and crevice corrosion, which are known weaknesses of 316L.

Rolex’s 904L “Oystersteel” goes even further, utilising 25% nickel and 4.5% molybdenum to combat corrosion, but as a result of the high nickel content some people experience contact dermatitis when wearing Rolex steel. Cartier’s choice of 316LVM seems like an excellent hypoallergenic alternative to Oystersteel, whilst still offering greater resilience and longevity than standard 316L. Some lucky owners of both the all-steel and the two-tone Santos have commented that 316LVM is visually different from 316L, as well. According to Watchuseek members @Pun and @Ducatiti, the all-steel Santos has a cold white tone, while the two-tone Santos has a warm cream tinge that plays nicely with the pops of yellow gold.

Two-tone 316LVM steel and 18k yellow gold Santos Large, ref W2SA0009. Image: © Cartier

And there you have it, all of the obscure technical information about the Santos that I’ve been able to uncover over the years. Hopefully this is of interest to some like-minded horology nerds out there, if for no other reason than to reveal that the Santos is a watch with a surprising amount of depth and watchmaking merit, and not just a beautiful object from a prestigious brand.

This Post Has 9 Comments

  1. Jason Swire

    Just an update on this post, Watchuseek member @johpe has found out some more info regarding the Santos’ warranted daily timekeeping performance, as well:
    “I asked about the accuracy of the Santos de Cartier and they stated +/- 10 seconds per 24h for the automatic 1847 MC movement (and within 1 second per month for their quartz movements). I can add that my Santos is about +1s / 24h.”

  2. Deb

    Does the Cartier Tank Must watch WSTA 0051 with the stainless steel band also use the 316L for their steel with 10% nickel?
    Is that considered hypoallergenic?

    Thank you –

    1. Jason Swire

      Hi Deb, thanks for your comment.

      Cartier use 316L steel for all their plain steel watches (aka, not two-tone steel and gold) which will include the Tank Must. No stainless steel alloy is hypoallergenic, although some are better than others when it comes to causing skin reactions. Rolex’s 904L ‘Oystersteel’ is the worst offender here due to the high nickel content (25%), while 316L is safer (10-14%). That being said, anyone hypersensitive to nickel will experience issues with stainless steel, no matter the specific alloy.

      For truly hypoallergenic watch materials, look for grade 2 titanium, ZR02 ceramic, 950 platinum, and tantalum.

  3. Chrono Brewer

    Very helpful insights for someone interested in a Santos. That antimagnetism is particularly great to hear. Thank you for the research.

  4. Hairstyles Men

    Admiring the time and effort you put into your site and detailed information you offer. It’s awesome to come across a blog every once in a while that isn’t the same out of date rehashed material. Fantastic read! I’ve bookmarked your site and I’m including your RSS feeds to my Google account.

    1. Jason Swire

      Many thanks for the kind words, much appreciated 🙂

  5. Nicole

    Thank you so much for this article! I’ve had trouble with my Rolex Datejust for YEARS and stopped wearing it because of the allergic reaction. I assumed it was all luxury watches. My husband bought me the Cartier Tank for Christmas and I’m optimistic the bracelet will work for me after reading this article!

    1. Jason Swire

      Hi Nicole, apologies for the delayed reply. I’m glad you enjoyed the article, and congrats on your upcoming Tank! Once you receive it please let me know if you find the steel to be easier on the wrist than your Datejust 🙂

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