What is a Hydrosol? Hydrosols are like essential oils but in far less of a concentration. Steam distillation is one way that we get both the essential oil from the plant and the byproduct of making essential oils, hydrosols. With steam distillation, plant material is added to the internal perforated drum of a still. In a separate drum surrounding the perforated steel, water is heated. As the steam pushes through the plant material, it causes the glands of the plants to burst and release the oils and essence of the plant into the steam. The oil rises through a condenser and collects in a separate vessel. This is what we know as essential oil. The fragrant water that was steamed with the original plant material is our hydrosol, or floral water.