Any colour so long as it's black. By Simon de Burton for The Financial Times

1 September, 2009

Followers of wristwatch trends will have noticed that many brands appear to be adopting the late Henry Ford's philosophy of making their products available in "any colour so long as it's black". We refer, of course, to the recent popularity of covering steel watches in a dark coating by use of a chemical process called physical vapour deposition (PVD).

It might make a watch seem cutting edge, but the process has been around since the 19th century when it was used by Michael Faraday, the chemist and physicist – although it did not become known as "physical vapour deposition" until 1966.

So what exactly is it and why is it considered to be a useful addition to a wristwatch? PVD essentially involves placing the item to be coated in an inert atmosphere, heating it to about 400 degrees centigrade and spraying it with molecules of whatever substance it is to be coated with to leave a thin film (around one micron) that is bonded to the object rather than merely applied to the surface.

Aluminium, silver, gold, carbon and graphite are all popular materials for use in PVD coating, which takes place in a large, heated chamber that can create a vacuum almost equivalent to that found on the edge of space. The best PVD machines cost up to £1m and are used to coat a vast range of objects, especially automotive and aerospace components.

The benefit of applying a PVD coating to a wristwatch is that it increases wear resistance by giving it a finish that does not scratch or chip easily and which covers even complicated parts, such as bracelets, smoothly and evenly. The quality of finish can, however, vary and, once breached, PVD cannot be repaired other than by re-coating the entire object.

Watch brands also use more advanced coating techniques such as chemical vapour deposition (CVD) which works through chemical reaction, and diamond-like carbon (DLC) which creates a virtually scratchproof surface using a synthetic material that is almost diamond-hard.

PVD, however, is the most popular and least expensive coating method and the "black look" that it creates has been adopted by numerous brands, including Tag Heuer, Audemars Piguet, Girard-Perregaux and Panerai to name but a few. Although many of the watches it is used on are bought on the basis of looks rather than performance, PVD coating has also become popular for military watches both because it is hard-wearing and, importantly, non-reflective.

One brand that has not used it is Rolex, a fact that is perhaps surprising considering it makes the best-selling and most actively used sports watches in the world. Various companies, including the London luxury goods store Bamford and Sons, offer used Rolex watches that have been given an after-market PVD coating, but Reza Rashidian, the big game hunter and luxury watch lover, has gone one better by setting up a business that supplies new Rolex models with the even more resilient DLC treatment applied.

Mr Rashidian hit on the idea about three years ago when he asked Kamal Choraria, the London watch dealer, to customise a Rolex watch in order to make it ideal for hunting – he specified a material strap rather than a metal bracelet, unbreakable, fixed lug straps, a non-reflective crystal and, in particular, a non-reflective black coating – DLC.

The completed watch attracted interest from a sufficient number of Mr Rashidian's friends and colleagues to encourage him to set up a business supplying so-called "Pro- Hunter" Rolex watches – new and unused models treated with DLC and, in some instances, featuring other subtle and practical adaptations. The watches are made in limited editions of 100 examples (500 in the case of the GMT Master) and have proved so successful that about 500 have now been sold despite being priced at 25 per cent more than the standard models and the fact that they are not approved, endorsed of warranted by Rolex and will not usually be accepted by Rolex for servicing.

Owners include former Bill Clinton, the former US president, Arpad Busson, the financier, Ray Floyd, the golfer,Michael Lynton, Sony Pictures entertainment CEO and gallery owner Tim Jeffries.

Last year, Antiquorum sold movie director Brett Ratner's Pro Hunter Double Red Sea Dweller for $30,000 in New York, almost three times more than the original price, and a similarly impressive sum was achieved by the house in June when it sold a Pro Hunter Cosmograph Daytona for $35,000, about 30 per cent above retail.

"I had the original Pro Hunter made because I had already lost two Rolex watches while I was crawling along the ground, stalking game," says Mr Rashidian. "The idea was to improve the usability of what is really a great tool watch while keeping it in line with the history of Rolex and avoiding any sort of perversion of the watches. Everything we have done has been done for a practical reason."

The Pro Hunter Rolex watches are available in several different models, the latest being a version of the anti-magnetic Milgauss. All come with a two-year Pro Hunter warranty with servicing available at a dedicated Pro Hunter workshop in London.By Simon de Burton for The Financial Times September 2009