Ultra-thin horology
Loyal to its pioneering spirit, Piaget began designing and producing ultra-thin movements right from the start. The famous ultra-thin mechanical hand-wound 9P calibre, presented in 1957 and measuring a mere 2 mm thick, was to leave an indelible and historical imprint on the watch industry. Three years later, Piaget launched Calibre 12P, the world’s thinnest automatic movement at just 2.3 mm thick, and described by the influential Journal de Genève as a “milestone event in watchmaking history”.

Thanks to their slenderness and their compact nature, these two mechanical calibres and their successors were to open up whole new vistas for Piaget designers, paving the way for all manner of bold creative moves including cuff-watches, coin-watches, shaped cases and hard stone dials.

Back in the 1960s, Piaget used stone as structural components and not just decoration. After making their first appearance on Piaget dials, jade, lapis lazuli and opal were then used on watch bracelets from the 1970s onwards.

This represented a revolution combining the nobility of hard stones with a broad range of colours and was perfectly in tune with the fashions of the time. Pure creative genius..... from "Groovy, Baby!" of the Stoned Sixties  to "May the Force be with you" of the Funkadelic 70s .

Now in 2013, Piaget returns to their stone dials that started the Swinging Sixties and Psychedelic Seventies. Let's see where the technique and aesthetic of Hard Stone Dials come together at Piaget.

LAPIDARY

A lapidarist is an artisan who works stone, mineral, and gemstones into decorative items, including cameos, or cabochons, and faceted designs. The specific techniques are tumbling, cabochon cutting, and faceting.

Another technique used is pietra dura or pietre dure ("hard stone" in Italian). It is also named 'parchin kari' in India. This inlay technique of using cut and fitted, highly-polished coloured stones to create images.

The stonework is glued stone-by-stone to a supporting material after having previously been "sliced and cut in different shape pieces. The pieces are assembled together so precisely that the contact between each section was practically invisible. Stability is ensured by making grooves on the undersides of the stones so that they interlocked, like a jigsaw puzzle, with everything held tautly in place by an encircling 'frame'. In Europe, the technique first appeared in Rome in the 16th century, to reach full glory in Florence. Many different colored stones, particularly marbles, were used, along with semiprecious or precious stones.

These stones are extremely fragile and hard to cut, which means that working with them requires a combination of controlled gestures and considerable dexterity. The extreme finesse of the cut-out shapes represents a major technical feat and calls for highly experienced artisans. Each stone reacts differently to the cutting operations and will look different according to its thickness.

Although the tools used to cut stone are now more advanced, the techniques of lapidary have not changed since primitive man created stone tools.  Although the market for ornamental stone has grown substantially over the past few years, the population of skilled lapidarists continues to shrink making lapidary a highly sought skill. 

Transforming rocks into ornamental stones is not easy.  Lapidary is a physically challenging artform. Apart from the physical danger of flying debris and sharp instruments, exponents are at risk of chronic lung disease from dust or fungal spore inhalation. A Master lapidarist must be proficient in practical material science and geology.  Mineral composition and the texture of rocks differ according to variation in geological history thus, physical properties are not standardized, not even amongst samples of the same species.

Such physical characteristics (elasticity, compressive strength, modulus of rupture, friability) are negligible when small sculptures are produced but they become important considerations when thin discs for dials are required.  Unfortunately some beautiful stones cannot withstand the internal stresses and strains that occur; for larger watch dials, delicate stones like Opal cannot be used.

One of the most important properties of lapidary material is the colour.  The color of a stone is a result of light rays that are absorbed or reflected in the material. Perception of colour is also influenced by the stone texture, lustre, transparency or opacity, size, inclusion patterns, and the source or type of light.  The real skill of lapidary is optimizing these optical properties.

The lapidary techniques required to manufacture a stone dial are sawing, grinding, sanding, lapping, polishing, and finally drilling.

The first step is sawing through the rough rock sample.  Ideally rough material should have good colour/pattern, uniform texture, freedom from large fractures, stains or unwanted inclusions. 

Some stones are extremely rare and seldom come to market in sufficient quality and quantity. Pietersite (variation of tigereye) for example, is extremely rare because it has been "all mined out", according to South African authorities. 

When sawing, lapidarists use a thin circular blade with its outer edge impregnated with diamond grit to cut through a rough stone sample.  A liquid such as oil or water is used as a lubricant and coolant to prevent thermal damage to both the equipment and stone. 

This initial step really determines the final appearance of the finished stone dial.  Cuts along different orientations or axes on the same stone may produce different color hues and patterns. An expert cut will not only enhance the natural color of the stone but by capitalising on the natural cleavage planes, the durability of the final dial can be increased.  By the end of this step, a large percentage of the original rough stone is wasted while yielding only enough material for a few stone dials. 

After cutting into thin sections, outlines of shape and diameter of the dials are made.  By grinding and sanding using finer abrasives each time, precise control over the shaping of the stone disks transform them into perfect circular dials

Lapping is the next technique.  Lapping removes material like sanding or grinding, except that sanding and grinding use abrasives that are fixed (bonded abrasives) whereas lapping abrasives are suspended in a liquid carrier, and are free to move about.  Performed on one side of a vibrating flat disk, lapping is used to create flat surfaces on a stone. 

The stone dial is sandwiched between the vibrating disk of the lapping machine and a weighted metal cylinder placed eccentrically to smooth out a specific portion of the dial.  The brown liquid is the abrasive while the number on top of the cylinder indicates the time required to flatten out the area of the stone disk.  A stone dial undergoes this lapping technique twice: once on the front and the second time to produce a parallel surface on the back. Using special techniques, lapping can achieve a flatness ratio of 12 millionths of an inch and parallelism tolerances of 50 millionths of an inch.

This caliper ensures that a dial has a uniform thickness of 0.7mm.  Uneven surfaces will introduce rotational forces (twist and bend) if the stone dial is screwed onto a base plate potentially causing cracks and destroying the dial.

Polishing achieves a mirror-like finish so that reflections off the surface can optimize its visual beauty.  Polishing requires knowledge of the hardness of the stone being used.  The harder the stone (Mohr's scale), the more difficult it is to polish.  As many types of fine abrasives are used (tin oxide, aluminum oxide, cerium oxide or red iron oxide), this step is mostly 'trial and error'.  Specific formulas of abrasives to be used with different types of stones to optimize its visual effect are trade secrets.

 

Here are the final stock dials made of different stones.

 Blue like the colour of the sky or the ocean, Lapis Lazuli is said to encourage harmonious relationships

Altiplano 24mm Stone Dial
18K pink gold case set with 48 brilliant-cut diamonds (approx. 0.4 ct). Turquoise dial, Piaget 690P quartz movement, black satin strap.
Numbered Edition
Boutique Exclusivity
Ref. G0A37207

Movement 690P is not your ordinary plastic mass produced chip-set.

There is substantial metal decoration, blue screws (even if you cannot see them) and Geneva Stripes on a mostly metal movement with 8 jewels!

Even for quartz movements, there is a standard of 'haute horlogerie' that Piaget subscribes to.