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A Day at HYT Part II: The Technical Part

HYT Watch Technology

HYT Technology

An HYT watch uses liquid to tell us what hour of the day it is. To do so, it uses a specially developed manually wound movement to power two bellows. It is these bellows that contain two immiscible (they do not mix) liquids; one coloured and one transparent.  The left bellow (as you look at the watch) is pressurised by the movement, concertinaing as this happens to push its coloured liquid up into the capillary. This liquid them makes its way from the left bellow to the right, gradually filling up the right-hand bellow with transparent liquid.

Once the liquid gets to 6 o’clock the liquid then reverses. This happens in all HYT watches, meaning they are classed as ‘retrogrades’ and is managed because it is at this point the movement releases the pressure on the left-hand bellow causing the liquid to flow back 12 hours to its starting position.

At first blush all this might seem a little obvious, maybe even easy. But it is only when you understand the precision and technology with which these watches are made that you come to comprehend what HYT has achieved.

The Bellows

Starting with the bellows, their walls are around a quarter of the thickness of the average human hair – 0.02mm and extremely delicate to the touch. It is the left bellow that exerts the pressure on the liquid within the capillary, requiring a movement of just 0.0015mm in order to push the liquid through one minute. Additionally, the amount of force required to do so is not constant; when the coloured liquid starts to move from left to right, the left bellow requires 0.1N, whereas at the end of the movement, prior to the retrograde action being performed, it requires 1N, 10 times the force because of the build-up in pressure in the both bellows.


Given the accuracy to which HYT works and the inherent propensity of liquids to expand and contract with temperature, this can have a serious effect on the system. Accordingly, HYT developed a ‘thermal compensator’. Without this ingenious component, their watches would have an inaccuracy of 3 minutes per degree (!), meaning that moving from Switzerland (at the time of writing it was 2 degrees), to Dubai for example (27 degrees) would mean the watch would be over an hour out due to the liquid’s expansion… clearly unacceptable! Instead, thanks to the thermal compensator, this is almost completely eradicated; an incredible technological achievement.

The Capillary

The capillary is just as high tech. Its inner diameter is 0.8mm, with a wall thickness of 0.4mm. The inside has a special transparent, hydrophobic (which means a molecule is repelled from water) and oleophobic (a molecule is repelled from oil) coating. This ensures both liquids pushed through the capillary can do so smoothly whilst leaving no trace of their presence – the last thing you need is to leave a smear on the inside, allowing gradual build-up of the dye not only ruining the look of the system but also affecting the accuracy of the timepiece.

Water tightness and air bubbles

Normally, watch manufacturers are working their hardest to prevent liquid from getting into their watches. In HYT’s case however, they have gone to great lengths to ensure it doesn’t get out! This means they have to work at a molecular level; if just one molecule of liquid escapes from the capillary system, then the piece is a failure. Accordingly, HYT works to approximately 10,000 times the tightness of a dive watch to ensure this does not happen.

The next issue is air bubbles in the liquid. If you have the opportunity to examine an HYT watch, you will see the liquids are touching seamlessly. This is only made possible because all air has been extracted from the system. For the last seven years (since their first prototype was launched in 2012, which itself took three years to develop), one HYT technician has been doing this by hand; adding the liquid to the system with syringes before then extracting the air through valves; a four-and-a-half-hour process PER WATCH. Once more, if this is not done properly, the watch will be deemed a failure and that time will be wasted; again illustrating the intensive nature of the process and the accuracy to which HYT works. Clearly continuing in this vain was uneconomical and so, for the last two years, three PHD engineers have been working on a robotic solution. Although it is yet to be put into production they have now, as of 2019, developed a machine to do this technician’s work, cutting that painstaking time to just 30 minutes.

And the length of time it takes to complete all these steps and assemble one capillary system?

Around three weeks . . .

So now we understand a little more about the technology behind them, that takes us onto the important question; are they actually worth both your consideration and your money?