EXCAVATION OF MARBLE IN CARRARA
The Romans quarried marble by inserting moistened wedges of wood into the natural fissures of the rockface. As the wedges expanded under the effect of the moisture, they forced the marble loose from the rockface. A slightly later technique, and for centuries the successor to the Roman method, was to drill holes into the face of the marble and then sledge-hammer metal wedges into them until the stone split. Depending on the proportions of the stone being removed, this technique was used to obtain formelle (when practised on blocks) and tagliate (when practised on huge stones).
The real breakthrough in marble quarrying came in the 16th century with the advent of explosives. Gunpowder was first used in the quarries of Carrara in 1570 – an event deemed so memorable that Alberico Cybo struck a special coin in its commemoration (a silver doubloon bearing the image of a flaming barrel of gunpowder and the legend – in German – Von Gutten in Pesser).
This so-called varate not only revolutionized the act of quarrying – it also transformed the surrounding landscape. The explosions opened vast gashes in the mountainside, which in turn led to the opening of new quarries: a process which ended up profoundly altering the landscape of the marble fields, which from then on has been constantly mutable.
After the introduction of dynamite in 1895 marble was now extracted using a wire saw. This saw was mounted on rig of pulleys and driven by an electric or petrol engine. With a mixture of water and sand as an abrasive, this saw could cut blocks of marble from the rockface in record time.
There were several advantages with this new technique: it avoided the fracturing of the blocks, reduced waste to a minimum, made later dressing of the blocks easier and, although costly, kept the quarry in workable shape.
One innovation tends to invite another, and just a few years later 1897 came diamond-point cutting and drilling, techniques which were used as follows: “With the diamond crown wheel driven by electricity, a circular cut can be made in the matrix to a depth of up to 20 metres, in this way permitting the removal of a narrow column of marble of equal length. However, this column has all the quality, spots and defects of the matrix it’s taken from.
It so happened, however, that due to the position of the mountainside it was impossible to drill tunnels: so the holes sunk by the diamond crown wheel served as guides for the drill bit, which opens the way for the wire saw.”
A few years later the first pneumatic hammers were being used in the quarries, and these new tools made it possible in one hour to sink a dynamite hole which would previously have required two full days’ work by two quarrymen (one to hold the pistolét, i.e. the long shaft at the end of which was a cutting edge, and the other to swing the sledge-hammer).
1910 marked a watershed dividing the developments recalled so far and those which would come later: for this was the year a huge hydroelectric plant was built in the region, bringing electrical power within reach of heavy industry at least. From this point on, human effort was quickly joined by various types of motors – diesel, electric, petrol.
Today, technology plays so big a part in marble quarrying in Carrara that it has not only joined but supplanted the work of man: with e.g. single-blade gang saws that can cut at rates of 60/90 cm an hour, and mechanical diggers of tremendous power.
There are currently about 270 active Carrara marble quarries, and it’s in these quarries that the world’s most advanced technology is used. Yet although there are hundreds of Carrara quarries, only a few yield the top quality marble so prized for its colour and texture. It’s from these quarries that Amso International mines the marble blocks which are later transformed into slabs, paving and revetment tiles, and made-to-measure pieces. Besides the Carrara quarries, Amso International also sources from many other Italian and foreign quarries to offer its clients a wide range of marbles and stones selected over the course of years of research and investigation.