As with many other changes in watchmaking trend, the technique of skeletonisation became popular because of economic circumstances—in the late 18th century, a shortage of raw material made it expedient for watchmakers to pare down the material used in the making of movements. At the same time, the fall of the absolutist French monarchy towards the turn of the century — with Louis XVI and Marie Antoinette its vilified main figures—ignited a reaction against the aesthetics of excessive ornamentation that had typified the preceding period. (The subsequent oppressive Reign of Terror under Robespierre in France probably did nothing to nudge European sentiment back towards the optimistic, Arcadian-themed and highly decorative time pieces in vogue during the previous regime.)
The spirit of skeletonisation is, at its most fundamental, the spirit of technicality. As strange as it may seem to us today, with our understanding of traditional skeletonisation’s elaborately baroque forms, the original aim of open working a watch movement was to throw the focus back on to the watch movement and the beauty of its construction—especially in the case of particularly complicated watches.
In skeletonisation, the plates and bridges of a movement are hollowed out to leave only the barest framework needed to hold the components together — hence the name of the technique. In order to accomplish this, holes are bored into the plates and bridges, then joined with lines cut by a jigsaw, there by removing the sections to be excised. The edges are then smoothed down and polished with a combination of files and abrasive pastes to create the delicate metal webs we observe in skeletonised timepieces.