Cocoons deflossing consists in removing the surrounding down of the external layers from each cocoon. This is done before the selection with special machinery.
This operation comes before the brushing and it is used to soften the skin of the cocoon and to allow water to enter it. In this way, the unwinding of the single thread becomes possible.
Initially, dried cocoons are put into a steam boiler, in which vacuum is produced so that water can easily get inside. At this point, cocoons are full of water and are placed in particular baskets made of inox net where, dragged by a rack, go through the whole path diving the whole retting-pit. The difficulty of this passage mainly consists in being able to adjust and control the water temperature and the duration of the operation, in order to soften sericin both in the outer and inside layers of the cocoon’s bark. Of course, it is very important to always consider the specific peculiarities of the cocoons’ lot we are dealing with.
The brushing is necessary for the research of the thread head and it is performed into the “batteuse” machine.
The previously boiled cocoons are poured out into a tub full of water, which has a specific temperature set through steam. In a corner of the tub, rotating sorghum’s brushes are placed. The brushes perform a rotating movement into the water where cocoons are hovering. Thanks to this peculiar movement, cocoons head-ends are collected. Then, these are loaded into the basins that rotate around the reeling tubs by the brushing worker.
The fake twist, “torta” or “tortiglia” in Italian, consists in a particular disposal of the raw silk thread. This is made by crossing the formatting silk yarn many times between two or more rollers, particularly in the lenght that goes from the yarn assembling to the reeling spindle.
The aims of the “torta” are many: first of all is necessary to remove most of the humidity from the yarn. The silk yarn, which goes out from the ceramic ring, is deeply soaked with water, a weight equal to the weight of the fiber. Thanks to the fake-twist, two third of this water is removed.
Moreover, the fake-twist has the power to seal the filaments steadily , so the cohesion of the yarn increases.
This feature is particularly important for raw silk yarns that are intended for special fine uses.
Finally, the fake-twist has a cleaning action on the yarn, so that many defects due to the filament and to the reeling process are removed. This occurs because, when defects are passing through, the fake-twist do break the yarn and the worker can remove the defective portion.
After the passage through the “torta”, the raw silk yarn itself is dried, sealed and cleaned.
The produced silk is usually divided in lot of 600KG each. Every single lot needs to be tested by a government agency, present in all the Chinese regions, which release the “Certificate for Raw Silk classification and conditioned weight”, recognized all over the world and fundamental for the export. For every single lot, the colour degree, the percentage of humidity (conventionally 11%) and the quality of the yarn are verified. For this reason, samples of small hanks, called baby skeins, are taken and used to be tested by the laboratories of the public agencies. At the end, the lots are classified basing on the obtained results. In particular, a score is given basing on a scale which can go until to 6A for the top qualities. Unfortunately, the Chinese classification method is not fully reliable, as a small quantity of silk is tested (few grams compared to the 600kg of the lot). In addition to this, the evaluation is made in a subjective way, the human eye, through the seriplane and black tables.
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