There is more to a watch than just the movement you put in it. Sure, putting a low-quality movement in a great-looking watch is a real shame, but putting an expensive movement into a poorly made case is even worse. A really cheap watch (the ones you might find at a Walmart) is probably made of pot metal – a mixture of predominantly zinc scrap metal moulded at a low melting temperature. Some watchmakers may even use 304 Stainless, which is more affordable but has lower corrosion resistance to salt.
We generally use 316L stainless steel on our cases. 316L is commonly used in the marine and medical industry due to its corrosion resistance. It also has a high Chromium content which adds the ability for it to be mirror polished, on top of the hardness and corrosion resistance.
That being said, we have historically given our watches a bead-blasted or brushed finish – focusing the watch on its intended purpose.
Aluminium is another metal we use for parts of the watch we want to highlight with dashes of colour, the bezel insert on the Tugela for example. Using a process called anodization, the aluminium is able to be dyed virtually any colour. This allows us to find harmonic flows in colour and form. Just because something is built tough doesn’t mean it can’t be easy on the eyes!
It is also far more resistant to wear than if it were painted.
Recently we used Titanium for the case of the Kruger chronograph. It is an extremely tough and light material, being 45% lighter than stainless steel, coming in multiple “grades” or alloys, with Grade 2 being raw unalloyed titanium.
This is the most affordable grade of titanium, but it does have downsides. For one, it is not very scratch resistant, which is why we added a scratch-resistant coating to the surface. More on coatings below.
Grade 5 Titanium can be used for watch cases, however it is more expensive and does require more time to machine due to the slow speed at which it needs to be cut.
Bronze is another excellent watch case material, and something that we are considering using in the near future. It also has excellent corrosion resistance, bronze was the go-to allow in the marine industry before stainless steel.
The colour of the bronze differs depending on the amount of Tin in the alloy. The beauty of bronze is that it develops a lovely patina over time, almost like it is aging with the wearer.
Often this means that the wearer develops an emotional relationship with the watch, like you’ve weathered the storm together. There are also health benefits to wearing copper (bronze is 88% copper, 12% tin), but we won’t go into that here.
Most watch materials can receive coatings that will change the appearance and/or scratch resistance of the base material.
Physical Vapour Deposition (PVD) is a technique for applying thin films of one atom (or one molecule) at a time onto a surface. PVD is generally used as a decorative coating.
For the ultimate protection against scratches and dents in the outdoors, Diamond-like Carbon (DLC) is the best option. Similar to PVD, DLC is a thin layer of carbon deposited on the surface of a metal. DLC is applied in a slightly different way to PVD – it requires Plasma Assisted Chemical Vapour Deposition (PACVD).
DLC provides some of the properties of diamond, including hardness, wear resistance and slickness. There are 7 forms of DLC though, with different costs and degrees of strength, depending on the amounts and types of diluents.
There are also hardness coatings that increase the scratch resistance of a material. As mentioned above, to increase the low scratch resistance of titanium grade 2 on the Kruger, we added a 1200HV hardness coating. To learn more about how Vickers Hardness is tested, check out this article.
Ceramic is extremely scratch resistant, and can be made to have very detailed engraving. The finish that is applied to the ceramic does change the brightness to a ceramic colour, as noticed when we went with a matt finish on the Kruger bezel insert. It tends to be darker the more polished it is.
The downside of course, for those of us who have been a bit butter fingered in the kitchen, is that ceramic can be easily cracked or broken. Colours are also limited – last we checked, ceramics were only available in black, maroon, dark blue, green, white and pink.
The Krugers ceramic bezel insert
The “crystal” or the glass that sits over the dial of a watch can be made of several materials. Some of these materials are: sapphire, mineral, plexiglass, or acrylic hesalite.
More affordable watches tend to use a mineral crystal, although these can be easily scratched. It’s worth nothing that mineral is basically plastic, and comes with the upside of clarity, but the downside of being easily scratched. And unlike plexiglass – which we will read more about below – the scratches can’t be buffed out like they might be with Polywatch.
Sapphire crystal, being the second hardest material to diamond means it is extremely scratch resistant, although it is the most expensive option. As with ceramic, sapphire does have one negative in that it can shatter if hit against a hard surface. Smashing the face of your watch against a rock at the wrong angle isn’t advisable, therefore.
But in case you do, don’t be too hard on yourself. We’ve all been there!
Sapphire is also highly reflective, which is why you will commonly see anti-reflective (AR) coatings applied to sapphire. For ultimate outdoor legibility, double AR coating (AR coating on the inner and outer surface of the crystal) is the best. We did this for the first time on our Aoraki model, and the results are impressive:
AR coatings. Left is the double-sided AR coating
One of the other major features of our watches is the knurled crown. You’ll recognise knurling from common tools such as a socket wrench, carabiner, or photography equipment, as it provides maximum grip while maintaining a simple geometric structure.
Generally, we have been quite creative with the case back designs of our watches. A watch can either have a solid (most often stainless steel) case back or a display (can be clear mineral or sapphire) allowing you to view to the movement inside.
There are a few different techniques that can be used to add a graphic to the case back of a watch. Laser engraving is the cheapest, but can appear faint depending on the quality of the laser engraving. Acid etching is preferred as it provides a deeper more professional engraving. This is how we engrave the logo on the side of our watch cases, the information around the case back and on our buckles.
Many of our models feature a detailed and deeply engraved image. This is created with a mould that is initially modelled in 3D.
3D model of the Benguela case back
Typically watches will have black rubber gaskets made of nitrile butadiene rubber (NBR). This is a well-used rubber, used in the automotive and aeronautical industry for things like hoses, grommets and other parts that work with oil. It is resistant to a wide variety of other chemicals including fuel and coolant. The downside of NBR is it’s relatives narrow operating temperature (-20℃ to 100℃). There is another type of rubber known as Viton, which has even better chemical resistance, and a higher operating temperature (205℃). This added chemical resistance is one of the reasons we use Viton for the largest seal on our watches – the case back gasket. Viton gaskets are green in colour.
The Viton gasket of the Tugela GMT
So now we’ve covered what materials we use to make our watches. In the next part, we’ll talk a bit about case construction. Thanks for reading!