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THE THREAD TWISTING AND THE ORIGIN OF THE SILK MILL
The silk threads consist of a cluster of very fine strands, and before being put into the looms to make cloth, they must be twisted to increase their cohesion and resistance.
At Bologna from the C 14th an intricate machine had been used for twisting: the round spinning frame. This machine, worked by hand, could process tens or hundreds of threads simultaneously. Subsequently a water wheel was attached, and at that point, the one room structures with small scale machinery were transformed into silk mills, that is buildings of three or four floors.
This method of production was introduced into Trentino in 1537, when the Bolognese master silk maker Cesare Dolcino and the carpenter Vincenzo di Giovanni de Fradino moved to Trento under the protection of Cardinal Bernardo Cles. These two, at the behest of the Prince Bishop, built a mill "alla bolognese" financed by some of the more influential families of the town and for this reason the following year they were condemned to death in absentia by the Senate of Bologna.
The manufacture of silk threads was not however very successful in the town of Trento, and attempts at production petered out in the space of a few decades. From the second half of the C 16th throwing mills (for twisting) using water power began to be built in Rovereto and Vallagarina. In this entire area, unlike the capital of the Prince Bishopric, the silk industry experienced exceptional growth. In a short space of time it became the principal local economic activity and exported its products all over Europe.
THE THROWING MILLS
The throwing mills in Rovereto, built to house the machines which did the twisting of the silk threads, had 6 or 7 floors each of a height of 2 metres. Thus the overall height of these buildings was roughly 15 metres so they stood out above the other buildings, giving the C 18th town a distinct skyline.
The wooden machinery was worked by a water wheel inside the building and driven by water from the millrace. The main elements of the throwing mills were circular frames 4-5 metres in diameter. The various reels and spools, loaded with silk, were fixed on the base of each frame. As they turned, they twisted the thread which was, at the same time, wound round the reels above. Every link in the process was called a pass ("valico" or "vargo"), and made up a unit used to measure the productive capacity of the mill.
The motion of the reels, spools and bobbins was generated by a central drive shaft, called a "plant", propelled by water.
The basic cell of the throwing mill was a square shaped module with 7 metre sides. It contained the revolving plant, the external circular frame and the space to move around it. This module could be replicated in series. The larger mills in Rovereto were made up of 3 modules alongside each other, all driven by the same water wheel.
The facades typically had a great number of windows, which provided the rooms with adequate light and air and which, in some cases, can still be seen today.