What is PVD? The definitive guide

Buffy Acacia

I could rant forever about stainless steel, and what a miracle it’s been for manufacturing in general. The only drawback of using stainless steel for a watch case is that sometimes you don’t want it to look like steel. In those instances, we turn to coatings. Prior to the popularisation of PVD in the ‘70s and ‘80s, cases were often plated or otherwise coated with gold to give them a luxury appearance at a fraction of the cost. Now, almost every watch with a coating uses PVD in a huge variety of colours including metallics like gold, basics like black, or even bolder options like solid red. But what is PVD, and why has it made the vast majority of alternatives redundant?

The history

It took over a century for a watch to be given a PVD coating, but the process itself was kickstarted by Michael Faraday in 1838, one of the the fathers of electricity. Among other things, he discovered electromagnetic induction, electrolysis, and diamagnetism, and without him our electrical generators, motors, and entire understanding of electrical power would look very different. His only intention was to discharge plasma from brass electrodes within a vacuum, but that vaporising was refined as the years went by. Robert Grove discovered sputtering in 1852, depositing some copper onto a polished silver surface. All of these developments became a little sidetracked however, with other technologies gaining popularity for their use in making mirrors.

The first use of the term ‘physical vapour deposition’ or PVD can be found in the book Vapour Deposition by CF Powell, JH Oxley and JM Blocher Jr. from 1966, and that’s around the time when PVD started seeing use industrially and commercially. Initially its greatest use was increasing the hardness and wear resistance of cutting tools, as well as mechanical components in the aerospace, automotive and firearms industries. As watches became much sportier and active from the ‘60s to the ‘70s, it didn’t take too long for the first watch to embrace PVD coatings. But first, let’s take a look at how it’s done.

The process

Physical vapour deposition is actually an umbrella term which can include several processes or variations upon the same concept, including sputter deposition, arc vapour deposition, and ion plating. Ultimately, the goal is to physically bond a thin film of material (known as the target) onto a part or parts (known as the substrate). There are many different ways to achieve this. In any scenario, both the target and the substrate are placed in a vacuum chamber filled with inert argon gas, then the target is heated or otherwise vaporised until it evaporates into a plasma. Then, when the particles collide with the substrate, a microscopic film is formed with much better durability than traditional electroplating methods.

Other variables include the thickness of the film, as well as the chemical composition of the target material. For example, you can achieve a gold look by actually using metallic gold, or you can get a very similar look with much better durability by using titanium nitride. For that reason, most gold PVD doesn’t actually contain any gold atoms at all. Titanium itself is highly versatile in PVD applications, and is also used to achieve that iridescent rainbow look. That kind of effect is generally frowned upon in watchmaking, largely due to its association with cheap knives, ‘aura’ crystals, and other trinkets which could be seen as tacky. Even DLC or ‘diamond-like carbon’ is also a form of PVD, but rather than metal, carbon is used to achieve a much higher hardness and scratch resistance. Clearly, the target material doesn’t always need to be metal, allowing for a versatile range of treatments including ceramics.

PVD’s evolution in watchmaking

The first known watch to use a PVD coating was the Porsche Design Chronograph 1 in 1972, evidently taking a leaf out of the automotive side of things. Black PVD became a bit of a staple among racing chronographs, leading to legends such as the Heuer Dark Lord Monaco from 1974. Admittedly, the PVD process still left a lot to be desired in those days, and the black coating could be scratched easily. The trend continued into the ‘80s, notably with the quartz powered Heuer Diver Professional, even if some of those PVD coatings have entirely flaked away 40 years later. Meanwhile, the technology was being rapidly improved in Asia.

Chinese and Japanese watchmaking boomed in the ‘80s, mainly thanks to the proliferation of quartz movements and the increased affordability of watches for consumers. By the mid ‘90s, gold plating methods had begun to be phased out with the introduction of reliable gold PVD. Just have a look at some of Seiko’s PVD watches from the ’80s and ‘90s, and you can see that they may be scratched to hell, but there aren’t as many huge patches of base metal visible through worn plating. In the last two decades, PVD has become the default industrial process for metal coatings. It has been refined to such a degree that it’s quite affordable, and applied films can be as thin as 0.3 microns, 266x thinner than a human hair.

PVD’s durability

Questions about the durability of PVD coatings are usually sidestepped by comparing it to electroplating, but that’s not entirely fair. Metal electroplating hasn’t fundamentally changed since the Victorian period, while PVD has been improved drastically. PVD coatings are bonded more securely to the base metal, they do add scratch resistance, and they will certainly last a long time. That said, they’re not invincible, and they’re not all created equally.

Coatings like DLC or Seiko’s Diashield are specifically applied to increase the hardness, but PVD applied purely for the colour may not be significantly more scratch resistant than the base metal. Whatever the target is made from will have a huge impact on durability, as will the thickness of the coating, and there generally isn’t a way to know what the thickness is without contacting the manufacturer. A gold PVD watch case may look pristine for many years, but a bracelet with many intricate, moving parts could wear away quite quickly.

Another consideration is that PVD can’t be polished, touched up or reapplied in any way, so any scratches and wear that occur will be permanent. For many, that contributes to the overall story of a watch’s life, but it may drive others mad. While a vintage watch with gold plating will probably show signs of wear, you can indeed use electroplating to restore it and look new.

PVD’s environmental benefit

If you look at what kind of treatments have been available for metals historically, you will realise that PVD is actually quite environmentally positive. In the treatment of construction and tooling materials, galvanisation has been incredibly common. It involves using zinc as a protective coating on steel, but the process requires several steps of bathing and washing in caustic chemicals, which can leech into the surrounding area or may be improperly disposed of. Even gold plating is undertaken in a bath of strong acid. Chromium, cadmium and nickel plating have also been known as a source of hazardous pollution for decades. The PVD process doesn’t even require large amounts of energy, and it doesn’t need any harmful chemicals beyond whatever the target material is made from. If environmental consciousness is important to you, then the mass acceptance of PVD can only be a good thing.