Abstract: The Apparatus for implementing the method of the invention comprises in succession, on the path of the thread (1): an air suction nozzle (3); at least one spray nozzle (4) for spraying a treatment bath; a removal chamber (5) for removing the air and excess treatment bath; and an air false-twist member (6); these four elements preferably forming a single-block assembly. In the spray nozzle (4) the treatment bath is sprayed at high pressure, e.g. of the order of 2×105 Pa to 6×105 Pa (2 bars to 6 bars) in the form of micro-droplets. After the apparatus, the installation includes finishing means (8) preferably consisting in two heater drums (10, 11) having offset axes, with the thread (1) being wound over the drums and moves over them in the form of substantially touching turns.