After owning the Sinn U1 All Black for some months (click here for a review), a ridiculous idea began to form in my head - I should buy another Sinn in PVD-Tegiment.
One day I found myself at the Sinn counter of the watch store. I accidentally paid for a Sinn 756 Schwarz Duochronograph, the store had no return policy so I had to take the watch home.
One of the strengths of the U1 All Black is its incredibly resilient case. Like the U1 All Black, the case of the 756S is Tegiment-treated steel PVD-coated with titanium aluminium carbon nitrite (TiAlCN). In typical watches the black TiAlCN coating will scratch and crack pretty easily, because of the disparity in hardness of the coating and the underlying steel; the TiAlCN layer has a hardness of over 2000 HV while normal stainless steel is rated at 200 to 240 HV. (HV refers to the Vickers Pyramid Number of the Vickers scale, a unit of measure for the hardness of a surface)
Sinn gets around this problem with Tegiment, its proprietary steel with a surface hardness of 1200 HV, close to that of the PVD coating. This prevents the usual scratching and cracking prevalent in most PVD-coated watches since the hardness of the coating “blends into the base hardness of the case”, according to the Sinn catalogue. So far my experience with both watches has been exemplary, neither shows a mark after many knocks and scrapes.
The case is not the only bit of cool technology in this watch. Embedded in the side of the case is a capsule filled with dry copper sulphate, which keeps the insides dry as well as indicates of the amount of moisture inside the watch case. The copper sulphate will absorb moisture inside the watch case, and as it does so it will gradually change colour from a white or light blue shade to dark blue. While I have no doubts that the copper sulphate does actually work, a friend of mine owns a Sinn chronograph that has had a dark blue capsule for nearly two years now, and is still running perfectly.
Another feature that ensures the integrity of the case is the D3 button technology. This allows the chronograph pushers to be constructed without the traditional tube and gasket, which can compromise water-tightness; instead a “doubly sealed” self-lubricated button runs right into the case. The button action is slightly firmer than on most Valjoux 7750 powered watches, which I assume is due to the pusher construction. That is most evident with the reset button, which usually operates with little resistance.
Despite the elaborate button technology, the buttons themselves are not Tegiment, neither is the crown. Thus they can be scratched, although I reckon that would be very, very difficult given their size and position.
Sinn also lubricates 7750 inside with Sinn Special Oil 66-228, a “high-grade, fully synthetic oil” which works at temperatures ranging from -45 °C to +80 °C. And of course this watch is can also withstand a magnetic field of up to 80,000 A/m, thanks to the soft-iron cage around the movement, a distinctly low-tech but effective idea.
The stylised magnetic field logo at 9 o'clock denotes the antimagnetic qualities of the watch
Black and white
Aesthetically the watch is nowhere near as fancy as the features inside. Based on the NaBo (Navigation Boardwatch) clocks found inside aircraft, the dial is stark and straightforward. Although the dial is very legible, the minutes counter of the chronograph is sometimes difficult to read because of the huge “12” marker. The date window at 4 o’clock is small but easy to read most of the time, because of the contrast between the white numerals and black background.
Sinn NaBo (photo from Sinn website)
I am sure the idea of brightly colour hands has been brought up many times. While I like that idea, I suspect the brightly coloured hands will draw attention away from the rest of the dial, making the time less easy to read. The current lack of colour is what makes everything stand out.
All variations of the 756 chronograph use the Valjoux 7750 sans constant seconds. Some find this disturbing since the whole dial is completely still unless the chronograph is engaged; I like it.
Under magnification the luminous material on the hour markers and numerals is quite inconsistent. Fortunately that is not evident in normal use because the white Luminova is actually applied onto an underlying hour marker outline which gives the marker its shape. Dials are one of Sinn’s weaknesses; my U1 All Black dial could be done better too.
Another criticism of the watch is its height-diameter ratio. It is not a large watch at 40mm wide, but at 14mm high it is quite thick. The perceived height of the watch is exaggerated by the relatively small diameter. On the wrist it looks fine, but in isolation the watch looks disproportionately chunky.
I purchased this watch on strap because the bracelet offered was ridiculously thin and flimsy-looking, especially for a watch of this size. The lack of an appropriately sized bracelet will definitely be a deal-killed for some potential buyers.
For all its flaws, this watch offers tremendous value for money. It is full of useful innovations, most notably the Tegiment case which is ideal for a watch meant to be worn daily. I foresee myself accidentally paying for another Sinn in the future!
(An alternative to this series of Sinn watches are the products from Damasko, which offers a similar tough case created with an ice-hardening process. Damasko was the case-maker for the first series of 756 watches before the partnership with Sinn was ended. However Damasko seems to deliver few watches at a very slow pace, so they are not widely available. Hopefully that will be enough to prevent another accidental purchase.)
The Damasko DC56 (image from Damasko site)
- SJXThis message has been edited by SJX on 2007-10-28 09:25:35