Bianchet Tourbillon B 1.618 Openwork Carbon Watch Review

by Jan 22, 2023Bianchet, Limited Edition

The Golden Ratio is prevalent in nature, architecture and in many other aspects of the world we live in, however, it is not usually the main focus when designing watches.

Fascinated by the Golden Ratio to create beauty and harmony in nature, Bianchet founders decided to use these proportions in their horological creations, in order to produce a contemporary, sporty and technologically advanced piece of mechanical art.

Bianchet is a young brand (founded in 2017) and has laid the foundation for inspiration through pure lines, using it’s passion for contemporary design and architecture, coupled with an intuitive sensibility nourished by Italian roots and Haute Horological techniques, to create the Bianchet Tourbillon B 1.618 Openwork Carbon.

Founder Rodolfo Festa Bianchet has a financial background; the brand’s main objective is to obtain a perfect balance between form and function using the Golden Ratio:

By combining the iconic Golden Number 1.618 and the work of Italian mathematician Fibonacci as design basis, coupled with a minimalist essential approach to watchmaking construction, Bianchet is about re-engineering a timepiece by applying the Golden Ratio to contemporary watchmaking. The B 1.618 Openwork is a contemporary Haute Horlogerie timepiece for the discerning watch lover with a refined, sophisticated-cool style, in search of a unique and very exclusive horological experience.

Bianchet Tourbillon B1.618 Openwork Carbon Orange

Bianchet Tourbillon B1.618 Openwork Carbon Orange

Face & case

There are various other colour and case material versions of the Bianchet Tourbillon B 1.618 Openwork available, however, the one pictured in this review is one of 4 colour options with carbon composite cases.

In all variations, the tonneau shaped case is 43(w) x 50(h) x 13(d)mm and in the carbon versions, the case is made from a composite of carbon and titanium powder, which has been finished by hand, with orange natural vulcanised rubber seals between case layers.

A relatively wide bezel frames a satin brushed black rehaut, which drops in and back towards the dial at not far off 45 degrees.  “SWISS MADE” sits printed in white at 6 o’clock.  A black chapter ring, with white minute markers and fatter orange 5 minute markers surrounds the dial, echoing the proportions of the rehaut.

The dial is heavily openworked and the movement skeletonised, therefore it is possible to see through the dial in many locations.  Made up of black satin brushed titanium arches, curves and circles, the floating skeletonized flanges and bridges of the movement, play with light and transparency to create a sculptural architecture, who’s design is clearly based on the Golden Ratio (read more about the Golden Ratio later).  

Many of the movement cogs and wheels are visible through the dial, in contrasting polished rhodium coated, providing additional contrast to the many shades of black angles within the dial.  Black and orange is very much the theme throughout, however there are also some subtle additions of polished steel, being the Bianchet icon discretely placed at the centre near 12 o’clock.  In addition, a polished screw can be seen in each corner of the dial and an additional 3 smaller rivets can be seen along either side, holding the dial frame together.  

The tourbillon takes up most of the dial area between the centre and 6 o’clock; it is shielded by a non magnetic titanium cage and sits behind one of the curved black titanium bridges.  It has a variable inertia balance wheel, which is fitted with four gold inertia blocks, which are used to regulate variation (increase/decrease) in rate of the movement of the balance.

The hour and minute hands are relatively wide, with rounded ends and hand applied orange lacquer along their lengths, whilst the small seconds indicator hand (provided by the 60 second tourbillon) is thinner, with flat ends and is solid orange in colour.

An oversized crown which is wrapped in textured vulcanised rubber, has a black end, with the brand’s logo embossed with a polished finish.  The crown sits between two quite prominent crown guards, each of which cover most of the area they are located in, are made in the same material as the case and screwed down with two polished screws in each.

Turning the watch over, we are met with more black and polished rhodium surfaces.  The carbon case back is secured by 8 x polished screws and features various laser engraved inscriptions pertaining to the brand, model and water resistance of 5ATM (50m) in the carbon.

The back side of the movement can be seen through the sapphire window, the circular design clearly includes the Golden Ratio as the main design inspiration again.  The black bridges are intertwined with various polished wheels and cogs, as well as various sized polished screws and a few purple jewels are visible too.

Bianchet Tourbillon B1.618 Openwork Carbon Orange Case Back

Bianchet Tourbillon B1.618 Openwork Carbon Orange Case Back


The Calibre B1.618 was conceived as a skeletonized movement; featuring symmetrical and asymmetrical elements, there is a natural balance created by using the Golden Ratio.

It is an in-house made hand would movement, adjusted to 6 positions.  Beating at a frequency of 3hz/21,600 vph, functions include hours and minutes, as well as small seconds via the tourbillon.  Users should expect up to 105 hours power reserve once fully wound.

The movement is crafted from grade 5 titanium and is able to withstand shocks of up to 6000G in all positions.  In order to reduce friction risks, lubricants are loaded with nanodiamonds, therefore increasing accuracy and durability.

All parts are exquisitely finished by hand, using mineral sands and natural fibres.

Bianchet Tourbillon B1.618 Openwork Carbon Orange Side & Crown

Bianchet Tourbillon B1.618 Openwork Carbon Orange Side & Crown


The strap is in natural vulcanized rubber, with a diamond dimpled texture and comes with both an all black strap and an orange strap with black edges.  The underside of the strap has the Bianchet “B” icon repeatedly (at 90 degrees to each other) embossed into it, with the brand name running up the centre.

A brushed titanium folding clasp with the brand’s icon stamped in the centre secures the strap.

Bianchet Tourbillon B1.618 Openwork Carbon Orange Strap & Buckle

Bianchet Tourbillon B1.618 Openwork Carbon Orange Strap & Buckle

Other stuff

Now for the geektastic part…

The Golden Ratio (Phi or ϕ) is 1.618 and it’s inverse is 0.618 – this is also referred to as the The Divine Proportion and is said to be at the centre of the beauty of the universe.  It can be found in some of the most beautiful things in nature and has been used in art, architecture and music for centuries.

The Golden Ratio is derived from the Fibonacci sequence.

The Fibonacci sequence is basically a set of steadily increasing numbers, where each number is equal to the sum of the preceding two numbers.  Starting from 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144 and going up infinitely.

In simple terms, as numbers get larger, the quotient (the number resulting from the division of one number by another) between each successive pair of Fibonacci numbers approximates the Golden Ratio (1.618, or its inverse 0.618).

So, by dividing each number by the previous number gives the following sequence 1 / 1 = 1, 2 / 1 = 2, 3 / 2 = 1.5 and so on up to 144 / 89 = 1.6179…. The resulting sequence is 1, 2, 1.5, 1.666, 1.6, 1.625, 1.615, 1.619, 1.6176, 1.6181, 1.6179.

Here is a visual explanation on how the Golden Ratio has been used in the design of the Bianchet Tourbillon B1.618 Openwork and may/may not help in understanding how the Golden Ratio can affect design principles:


Bianchet Golden Ratio

Bianchet Golden Ratio

As you can see from the image above, the design was not by accident, but based on the Golden Ratio and it’s calculative method of design.

Many things in nature also have dimensional properties that adhere to the golden ratio of 1.618 and now you are aware, you may notice it in everyday things you may never have noticed before – now that you are aware of its existance, there could be a good chance you may now notice certain things looking visually proportionate to the Golden Ratio.

Bianchet Tourbillon B1.618 Openwork Carbon Orange on the Wrist

Bianchet Tourbillon B1.618 Openwork Carbon Orange on the Wrist

Our verdict

When I first saw the Bianchet Tourbillon B1.618 Openwork, my first thought was that it was beautiful, but I had no idea that the Golden Ratio was the reason for the seemingly perfect proportions. 

On first meeting founder Rodolfo, we sat down and he started talking through a power point slide show and asked if I’d be interested in learning how the design was based on the Golden Ratio.  As someone who studied both maths and design as a student, I was genuinely interested and he did seem quite pleased to run through the theory and how it is linked to their design.

So, the mathematical theory clearly works and the result is definitely to my personal taste.  I really like the shape of the case and the fact the movement is so heavily openworked and hand finished in black titanium, just adds to the drool factor.

On paper, you would think that the dimensions would make appear large, however, on the wrist, it doesn’t; it looks right, fits perfectly and is really comfortable.  With a weight of only 44 grams, one could easily forget that it was even being worn.  Even though it is so lightweight and the movement is resistant to 6000G, I doubt I would wear it to do high impact sports, although it has clearly actually been designed as a real wearable sports watch. 

My only negative comment, is that I’m generally not a fan of rubber straps, however, as in the Franck Dubarry Crazy Wheel, contact with the skin is broken up by the embossed logo pattern, which seems to reduce discomfort for me personally; many prefer rubber straps, so it could be a mute point for buyers.

At 13mm, it’s neither slim, nor too chunky, but the smooth edges and the fact the shape follows the curvature of the wrist, means that it will not really cause too many hassles with cuffs.

Being a relatively new brand, with only 21 pieces of each version being made and with a price of 55,000 CHF, it’s unlikely owners will come across another one out on their travels, but if they do, it’s almost certain there would be a nod of recognition, as this is certainly a watch for collectors who know what they appreciate.

On a side note, Bianchet offer a 5 year guarantee, which is a longer period than most haute horology Swiss brands; they are obviously confident with both their build quality and micro engineering, so should give a bit more optimism in taking a “punt” with the relative newcomer.

I am keen to see what comes next from Bianchet and whether they decide to use close correlation to a different mathematical theory… perhaps some fractal geometry could be their next design inspiration!?