Steam distillation is the most common way to extract aromatic compounds (essential oil) from a plant. During the steam distillation process, steam passes through the plant material. The combination of heated steam and gentle pressure causes the essential oil to be released from microscopic protective sacs. As the vapor mixture flows through a condenser and cools, it yields a layer of oil and a layer of water. The essential oil rises to the top and is separated from the hydrosol (floral water) and collected.
Some have asked about the difference between first distillations in comparison to complete distillations. The temperature for steam distilling is usually between 140–212 degrees Fahrenheit. Since different plants require different pressures, times, and temperatures, using this particular distillation method makes it possible to adjust the temperature based on the plant type, making it a very effective and precise way to obtain the purest compounds.