A mystery set ruby and diamond peony clip by Van Cleef and Arpels.

In the annals of grand, old jewellery houses, Van Cleef and Arpels is a relative newcomer.  The maison was founded in 1896 by Alfred Van Cleef and his uncle Salomon Arpels and right from the very beginning they were preoccupied with invention and innovation, which became the hallmarks of the brand.  Historically, they are well known for their transformable pieces, their Cadenas padlock wristwatches and their technically accomplished zip necklaces.  But their pièce de résistance and crowning achievement is the setting technique known as the Serti Mystérieux, or Mystery Setting.

Masterclass in setting: Perroque Mysterieuse clip by Van Cleef and Arpels.  They have become so proficient in the art of invisible setting that they can now achieve it with all sorts of shapes and cuts.  Note the rendering of the feathers in cabochon stones.

It is named so because the technique allows large areas to be set with small, square stones with seemingly no metal in between holding the stones.  The theory is relatively simple: a lattice is created which is criss crossed with tiny wires no more than 0.2mm thick.  Grooves are then cut into the sides of stones which are then slid on next to each to each other, creating the illusion of invisible setting.

The practice is more complicated.  It requires quite a large team of craftsmen to put a single piece of jewellery together.  For the best possible effect, the stones must all be evenly matched in colour, so it is up to the gemmologist to assemble the stones.  The lapidary must then cut each stone precisely so that it fits exactly in its allocated place within the jewel- if the stone is out by even 0.1mm not only will it rattle in its setting, but a gap will show too.  The master goldsmith will then set and assemble the piece.  It takes a minimum of 300 hours to construct each piece and for that reason only a limited few are made every year.  The preferred stones for this technique are rubies and sapphires because of their hardness- emeralds are tricky, soft stones, requiring even more labour, and it was only in the 1990s that the technique was perfected for diamonds.

One of the earliest pieces of invisibly set jewellery by Van Cleef and Arpels, the technique now adapted for rounded surfaces.

Gold box from the 1930s by Van Cleef and Arpels.  Initially, the invisible setting technique was only suitable for flat surfaces.

The setting was first used in the 1920s and a patent for the technique was filed in 1933.  At first, it was only used on boxes, compacts, cigarette cases and so on as mystery setting was only really viable on flat objects.  Other forms of the setting had been used by Chaumet and Cartier and patents had been filed accordingly, but they were never used in a widespread manner by these houses.  As Van Cleef and Arpels became more proficient, the technology was adapted to three dimensional objects and jewellery.  Since the beginning of this century, the jewellers have developed the Navette Mystery set, which uses marquise cut stones to cover surfaces, and Vitrail Mystery which plays on the stones’ transparency.  The mystery setting technique remains the pinnacle of achievement in jewellery making.

A skilled VC&A craftsman slides the specially cut stones onto the rails of this brooch to create the illusion of invisible setting.