Anti-reflective coating

Information and detection of a glareproof coating on a watch.

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It is not uncommon for well-made watches to come with an anti-reflective coating on the glass.

In the case of Breitling for example, this comes as a thin layer which blocks most of the unwanted reflections. Those coatings actually block colors selectively, so that the eye will not be annoyed by the most common reflection hues from the environment. That is why their crystals sometimes appear blue.

Is an A/R coating damaged?

New A/R coating from the Breitling SuperOcean

In fact, on the current Breitling models, this layer is applied both on the inside and the outside of the crystal, as both surfaces cast reflections. An outer A/R coating makes the watch even more legible; however, its major drawback is that it can be scratched. In addition, this process is known to be expensive. It is usually done in large batches of crystals at the same time, and then definitely not cost-effective to do on a single damaged glass.

Let us have a look at a beaten-up crystal from the same kind of model (which, incidentally, has a blue dial, so that they will not be mistaken in this experiment).

Breitling SuperOcean without outer A/R coating

The trick is to place the watch in front of a fixed, small light source and check its reflected color.

From the observation, it is obvious that the blue-dialed watch has no more glareproof coating.

New A/R coating from the Breitling SuperOcean

In the picture above, one can see that I used a standard undiffused light bulb, inside a dark room. Notice how the bulb's reflection is blue and dim when reflected by the A/R coated glass.

Breitling SuperOcean without outer A/R coating

On the other hand, in the second picture with the missing outer anti-reflective coating, the bulb now appears very clearly.

This observation technique works well on domed crystals, where the inner and outer reflection/refraction are distinct; however for flat sapphires, this is not that obvious, and I need to do more research. Maybe the naked eye is just not sufficiently accurate. If you have any suggestion, as usual, feel welcome to contact me.