delivery duct 10 which is connected to the inside of the various vats 1 which are mutually interconnected so as to define in practice a communicating vessel the homogenation of the bath is obtained in this manner said homogenation is also increased by the movement of the fabric which is subjected to continuous ascending and descending passes which keep the bath of each individual vat in motion as previously mentioned the feeds of the intensification baths are performed according to the amount of yarn to be dyed and according to the required color all of the above is calculated in kg h as regards the yarn taking into account the speed of the dyeing line it should be stressed that the dosage of the feeds of the main bath and of the reduction bath is performed immediately after the delivery of the circulation pump and this allows correct distribution in each individual vat avoiding the forming of different situations of chemical equilibrium in the various regions of the dyeing bath the bath cannot be prepared beforehand since it needs the intensification feeds and the dyeing bath or main bath maintains for the entire duration of the operation of the machine its own distinct composition of soda sulphinate and indigo also by virtue of all the active recirculations when the machine stops the feeds and the recirculations also stop and the composition of the dyeing bath rapidly changes mainly in its sulphinate component and also to a lesser extent in its soda component due to these variations it has been observed that the skein dyeing tested so far was unable to provide satisfactory results since it was not possible to keep the parameters constant and consequently obtain uniformity in the dyeing of the skein the invention.