Home steam distillation is used to separate volatile or organic compounds that would be altered by heat (like essential oils). It does this by forcing steam through the substance, thereby lowering the effective boiling point for the compound that you which to distill. Let’s go over a simple way to create your own home steam distillation system.
First, you need to understand how steam distillation works. The steam is generated in a sealed container (the boiler) by adding heat to water, then flows to a separate container via a tube. It is important that these two containers are separate as the heat used to generate the steam could decompose any essential oils you are trying to distill. After passing through the original material the steam passes through a condenser which uses water to cool the steam. What is left is condensed distillate.
Home made steam distillation systems come in many forms. The simplest is a pot of boiling water which is completely covered by a inverted lid. Inside the pot is a mesh or colander to keep the substance separate from the water and a cup to collect the distillate from where it drips off the handle of the lid, which is itself full of ice to cool the steam. It can't be used to distill much and the quality is not very good. However, you can build a better home steam distillation system with a little work.
To build a boiler simply use a tea pot or any metal contain that can be sealed to force the steam out one way. Next build a column out of pipe that has a connection at the bottom for the steam to enter and another on the opposite end for the steam to escape. Use pipe fittings that can screw on and off, because you will have to be able to open the column to fill it with your original substance or mixture.
For the condenser on your home steam distillation system you will want to create what is known as a counter flow condenser because it is much more effective than a normal water condenser and not much harder to make. To build it, select two lengths of tube that are different diameters so that one fits inside the other. Next affix the two pipes together in such a way that the steam can flow through the inside pipe, while water is flowing through the outside pipe. The counter flow condenser should sit at an angle while in operation, wherein the water flows upward while the steam flows downward in the direction of the collection cup. This step can be tricky and will take trial and error to eliminate leaks but once done you have your steam distiller ready to use.