Our Watch Specialist Jack Austerberry talks about patina of watches
Let’s talk patina, firstly, a common misconception of pronunciation, the word is pat-in-a, as opposed to our friends in America who pronounce the word pat-een-a.
So, within horological study, what is the difference between patina and damage? It’s a very difficult question to answer, because patina normally is a bi-product of damage…
In many cases, when talking about patina within a watch, people are referring to any part of the watch that has luminous compound applied; that’s the paint applied to the dial so it glows in the dark. Now, we have three categories of luminous compound: Tritium Isotope, Radium Isotope, and modern ‘Luminova’.
Radium was popular up until the 1920’s when it soon came to light that it was an incredibly harmful material for ‘the radium girls’ to be painting dials with, the uranium decay product derived from carnotite ore has a half-life of 1602 years, which makes it a little risky when inspecting a dial as inhalation of radium dust could leave you with necrosis… leave that bit for me to do!
Patina: Radium had a tendency to ‘burn’ the varnished top layers of older dials, so we can often see a spiral ‘radium burn’ on dials within the radius of the hands, if the hands have been stationary for an extended period, then you may notice radium burn reflecting the shape and position of the hands throughout the period (see fig.1).
Post the glowing Radium period, we saw the use of tritium become popular in the 1960’s, in 1968, radium was banned altogether. In view of the fact that tritium was used up until the 1990’s, we are able to produce more in depth studies over a much larger collection of watches. Whilst it may seem counter-intuitive; it is generally understood that tritium that has been exposed to little-to-no sunlight [or UV light] will produce a dark, creamy yellow patina. On the other hand, if a watch is exposed to large amounts of sunlight it tends to have a bleaching effect. Exposure to moisture/humidity is widely regarded as a catalyst for the patination and discolouration. That’s right, water damage. See fig. 2 for an example of an evenly patinated tritium dial.
The Tritium era came to a halt in the mid-to-late 1990’s, when it was realised that artificial luminous compounds could be created using strontium aluminate , essentially meaning our watches could glow in the dark without the need for a radioactive compound. Not only does this eliminate any potential risks to those involved with the manufacture of these watches, the new compound should provide more long term luminosity than the compounds previously used; tritium only remaining completely luminous for approximately 12 years, and Radium is known to have remained luminous for as little as that, whereas Luminova show little signs of long term decay; after exposure to light the phosphor within the compound will initially glow enthusiastically, settling down within an hour to provide a [legible] fainter glow for about 5 hours, whilst there haven’t been long-term studies on the actual (as opposed to radioactive) decay of Luminova, from my own experience, I would suggest that over a period of 5 years, it would appear that the Strontium Aluminate (or indeed the Europium reactive element that is used as a reactive binding agent) shows signs of long-term fading, eventually providing little phosphorescent longevity compared to when new.
Patina isn’t just found in the luminous compound, though. Patina isn’t something that can be easily manufactured, it takes time. In order to identify patina, one must be entirely subjective. An interesting trend within the watch market has been that many collectors are no longer seeking to find a watch in new old stock ( or NOS ) condition, but a watch that has acquired a natural patina over many years of regular use; a piece that has been has been well maintained over its years of life.
One might argue that this Wabi-Sabi outlook on watches, that’s watches that show the gradual destruction of time, have become appealing to collectors. A watch that isn’t trying to hide its potential flaws and, most importantly, has not been restored at any point.
To conclude I would suggest that it is quite conceivable that future market trends mights be dictated by the collectors drive to seek natural overall patina and watches that are in ‘honest' condition.