An effective way to prepare herbs for topical use is to infuse herbs in oil so that the properties of the plant can be extracted into the oil. Basically this means covering fresh or dried herbs with oil and allowing them to sit in the oil for a length of time and then pressing out the plant material. The oil then can be used directly on the skin, or used in a lotion or salve.
Below are a couple of different methods for making an infused oils. Some common plants used to make these oils are calendula, comfrey, plantain, St. John’s wort, cottonwood (poplar) buds, arnica, rosemary, chamomile, and lavender.
Although I am focusing in this article on herbs for topical use, you can use this same recipe to infuse herbs in oil for cooking with, such as rosemary, basil, garlic, and lavender.
Stovetop (Quick) Method:
Use a double boiler or a metal bowl sitting over a pot of water or a heat-tolerant measuring cup partially submerged in water in a pot.
Cover herb of choice with just enough oil to cover and bring the water beneath the container to a hot temperature, below a simmer. Heat the oil for 60 minutes or more, stirring often and not allowing the oil to bubble/boil.
Slow Macerating Method:
Add ~ 1 – 2 ounces (30 – 60 grams) of dry herb (ideally ground or chopped into smaller pieces) in each cup of fixed/carrier oil in an uncovered container or in a crockpot/slower cooker at its lowest setting, a dehydrator, a yogurt-maker, etc. finding a temperature of 115-120 degrees. You can also try placing in the oven on the “warm” setting – very low heat. You may need to leave the door of the oven open. Using a cooking thermometer, check that the oil heats to between 115-120 degrees (F). Allow to macerate for at least 3 hours and up to 14 days at this low heat, checking the temperature and stirring frequently. For fresh herbs, the heating method works great to evaporate off the water and discourage spoiling.
You can also macerate the herbs in oil in the Sun. For fresh herbs, you must allow for evaporation of water, so cover with a screen or cheesecloth in a jar in the sun.
In order to use and store the oils, carefully press out the plant material and preserve the oil. Allow to sit and separate from any water that may still be in it and pour the oil off into a bottle, being careful to allow no water into the bottle. Store away from heat and light.