A hair treatment method, including the step of spraying onto the hair a composition for changing the form of the hair, notably a permanent-waving or curl-reducing composition, using a device, called a low flowrate device, comprising at least two nozzles oriented such that their respective jets collide, these nozzles being supplied with said composition at pressure, the total flowrate of composition delivered by the nozzles being between 0.1 and 3 L/min, preferably between 0.2 and 2 L/min, and even more preferably between 0.3 and 1 L/min.