Extraction of Marble , yesterday and today
EXTRACTION OF MARBLE IN TIME
During the Roman period and at least until 1700 the mining was done manually. To
remove the marble from the mountain relied solely on the strength of the arms of
the workers because there were no machines that could come to their aid: they
used only wooden wedges planted with the tip and mallet cracks where the marble
was softer.
Following the wooden wedges were soaked by making, with the increase of the
volume, tear off the marble from the mountain. Then
the wedges of wood were replaced with iron wedges, below and above who were
admitted to the laminations of iron were beaten with heavy clubs to which you
obtained the penetration and the subsequent detachment of the marble from the
mountain.
Around 1700 began the first excavations by means of explosives (black powder)
that was introduced in holes made in marble with a chisel tip rod with forged. While
an operator holding this rod in contact with the point to be drilled, other
workers will beat with the bat and with every bit the rod was rotated a few
degrees in order to facilitate the penetration and dig a deep hole which was
then filled with black powder . Lighting
the fuse, the explosion took place which produced the separation of the piece
from the mountain.
This technique killing with explosive was called "launched" and although it
allows to reduce a large amount of rock in a short time, had the bulk defect to
destroy most of the marble escavabile and to produce a large amount of waste
Once detached from the mount the piece of marble was brought with the help of
crowbars in the forecourt for squaring. This
operation consisted in removing the tip with a mallet and the bumps on the sides
of the block to make it most suitable form of transport and to highlight the
quality.
It was later used a hand saw which consisted of a toothed plate at the ends with
two bands that were resting on the shoulders of the workers; them, by sliding
the foil with alternating movement on one side of the block, with the help of
water and sandriquadravano
siliceous marble with less fatigue and more accuracy.
Towards the end of the 800 quarries of Carrara and then also in quarries portoro
of our territory, was introduced a new technique, the wire spiral, driven by a
motor, allowed to cut the marble directly from upstream.
Once you have located a block to detach and liberatolo from one side to the top
of the material of little value with charges of dynamite were inserted in the
channels thus formed the uprights carrying the sheaves for the return of the
wire.
The helical wire had a diameter of approximately 5 mm and was formed by the
winding in helical form of three small steel wires (strands) with the
characteristic to change the sense of screwing every 50 m, so that the cutting
of the marble happen straight . This
wire had a length of 1,000 m, passing on the marble to be cut with an abrasive
mixture of water and silica sand cut marble. It
was not the thread to cut the rock, its only function was to transport the
helical groove in the mixture of water and silica sand: it was rubbing on the
surface of the marble that it corroded very small particles.
The squaring of the block was made with the helical wire.
The arrangement of the wire (the spread), however, required time, highly skilled
workers (the filisti) and large quantities of silica sand that had to be
transported from the quarries from Lake Massaciucoli, near Viareggio, where it
was extracted.
EXTRACTION OF MARBLE TODAY
In the early '80s there was a great innovation in the excavation of marble: the
use of diamond wire cutting.
The diamond wire is made of a steel cable on which are threaded rings coated
with diamond powder spaced from each other by small springs; this wire looped
around the boulder and spun by a motor, size in a short time the marble . To
pass the diamond wire around the stone to detach from the mount, you need to
drill holes in the vertical and horizontal must intersect with a drill capable
of drilling to depths of several meters.Contrary
to what happened with the coil wire, the cut is now performed by abrasion of the
diamond powder without having to resort to the use of silica sand. The
water has the function of cooling as well as serving to take away the residue of
the marble.
To detach easily from the upstream bank cut by diamond wire cushions are
inserted inside the metal as you pump air or, better, water under high pressure
by inflating the cushions themselves move the boulder from the mountain just
enough so that with the 'aid
of hydraulic jacks and excavators can proceed to roll.
Another machine used to remove the rock and also for squaring the block is like
a giant chainsaw (such as cutting wood) consists of a large chain saw with a
diamond teeth which penetrate the marble gets a wide slot with 5 cm .
