Rolex’s position at the top of the horology tree has been maintained for generations by a combination of ageless, enduring designs coupled with a practically unrivalled commitment to innovation. They have been responsible for a number of the most important revolutions in watchmaking since as far back as the 1920s, with their invention of the waterproof Oyster case, followed by the Perpetual self-winding movement a few years later. It is a pattern of ingenuity that continues to this day. The brand continuously pushes the boundaries of what is possible—and nowhere more so than in the engineering virtuosity inherent in their movements. One of the biggest leaps forward of the modern era arrived in 2000, when the Daytona received its first ever in-house built caliber, the Cal. 4130, complete with a new type of hairspring, known as the Parachrom.
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A watch’s hairspring, really the beating heart and regulating organ of the movement as a whole, has existed in an almost unchanged state since it was conceived in 1675.
This unfathomably thin coil of wire, set in the middle of the balance wheel, forms what is known as the balance assembly or, alternatively, the oscillator.
It is the hairspring’s job to make sure the balance wheel undulates back and forth at a precisely controlled rate, locking and unlocking the escapement’s pallet fork and so advancing the gear train, and eventually the hands, a set amount with each impulse.
It is one of the most crucial determining factors of any mechanical movement’s accuracy, and the manufacturing of the component is subject to incredible tolerances. An imperfection of merely one micrometer in its construction will lead to a watch running fast or slow by up to 30 minutes a day. As of 2015, Rolex guarantee timekeeping precision of +2/-2 seconds a day.
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Because of the extraordinary difficulties in creating hairsprings, there has been a virtual monopoly on them in the watchmaking industry for decades, with Swatch-owned Nivarox supplying just about every manufacturer, including Rolex themselves.
The Swiss firm creates their alloys, also called Nivarox (standing for Nicht Variabel Oxydfest, or Non-Variable Non-Oxidizing), in a range of grades, numbered one to five, with one bring the highest quality. Formed around a stainless steel base, high concentrations of nickel, cobalt and chromium are added, along with smaller amounts of titanium and beryllium. Only grades one to three are used in the watchmaking industry, although Nivarox also supplies the medical field, among others, with alloys used in extreme precision surgical implements.
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With the frequency of a caliber’s hairspring required to keep absolutely constant regardless of the ambient effects of temperature variation, magnetic fields and vibrations, the constituent parts that make up the Nivarox alloy have been chosen specifically—for their naturally hard wearing, antimagnetic properties and low rate of thermal expansion.
But while they may be deemed good enough for the vast majority of watch brands, Rolex felt there were still ways to improve.
The name Rolex chose for their own concoction is a portmanteau, made up of ‘PARAmagnetic’ and the Greek for color, ‘CHROM’.
The end result of five years of tireless work by the company's army of metallurgists, physicists and engineers, the Parachrom hairspring is made up of just three fundamental ingredients—niobium, zirconium (the two actually sitting side by side on the periodic table) and oxygen.
85% of the composite is niobium, something usually only found in tiny amounts in other alloys. It is one of the five major metals with extreme resistance to heat and wear, what are known as the refractory metals (the others are rhenium, tungsten, tantalum and molybdenum). It is more commonly used in jet engines for that exact reason.
As for zirconium, making up the other 15%, it is commonly found in things like catalytic converters and heat exchangers. It is easily malleable and highly resistant to corrosion and is also used as a hardening agent in steel alloys.
The final element, oxygen, forms as a layer on the niobium when it is exposed to the air, and changes color depending on the thickness of the coating.
All added together, they make the Parachrom hairspring completely unaffected by magnetism, effectively 100% impervious to temperature changes and up to 10 times more shock resistant than even the best from Nivarox.
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Five years after Rolex introduced the Parachrom hairspring to the Cal. 4130, the chemistry was altered to increase the oxide coating’s thickness to between 50-100nm. It was originally done to make the spring even more stable, but it had the secondary effect of it turning blue once it reacted with the air. Whether a happy accident or not (doubtful, seeing as how this is Rolex we’re talking about) it was adopted as the brand’s alloy and given the name the Parachrom Bleu. Since then, it has been steadily introduced across the entire portfolio, one of the very last parts of any of their watches to have been brought completely in-house.
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Like all the metals used in their cases and bracelets, Rolex’s hairsprings are created in their own foundry, deep underground in the central Plan-Les Ouates laboratory in Geneva. Here, the niobium and zirconium are fused together in a high vacuum environment, at around 2,400°C.
The two metals are passed through a specially built electron bombardment furnace three times, under 5,000 volts, with a carefully controlled amount of oxygen introduced.
It results in a ribbon of wire 30cm long and 10mm in diameter—weighing less than a pound, it can make up to 10,000 hairsprings.
A die press then transforms that into a strip some two kilometers in length and 1/10th of a millimeter thick. A final pass creates the finished product, with its rectangular cross section, and it is cut into 22cm sections.
Once wound and given a Breguet overcoil, its shape is fixed with a thermal vacuum treatment. The whole process takes several days, and variations in the spring’s thickness along its entire length have to be kept to within 0.1 microns, or about 1/1000 the width of a human hair.
It is the peak of precision engineering and a massive achievement, even for so seasoned a campaigner as Rolex. The brand’s dedication to advancing the art and science of watchmaking is what has kept them on top for so long, and nowhere is that more in evidence than with their Parachrom Bleu hairspring; what they themselves call the ‘guardian of time’.
Featured photo credit: @zimmermanwatchrepair