Hydro Diffusion method for extraction of oils is a type of steam distillation and is only different in the way in which steam is enters the container of the still. In hydro diffusion, steam is fed in from the top onto the botanical material while in the case of steam distillation, steam is fed from the bottom. In this way the steam can saturate the plants more evenly and in less time than with steam distillation.
The condensation of the oil containing steam mixture occurs below the area in which the botanical material is held. The main advantage of this method over steam distillation is that less steam is used hence shorter processing time and therefore a higher oil yield. This method is also less harsh on the botanical material.