Not all infusions are made solely with water. Infused oils are perfect for external use such as in massage oils, creams and ointments. There are two methods for extracting active herb ingredients in oil: cold infusion and hot infusion.
Cold Infused Oil – Pack as much herb material into a clear glass jar as you can and cover with oil (vegetable or olive is fine). Seal tightly with a lid and place in the sun, or another warm place for 2 – 3 weeks. After that, strain the infused oil into a dark glass bottle. The oil is ready for use straight away and if stored away from direct light will last for up to a year. To increase the strength of your infused oil you may repeat the process by packing a jar with new herbs, covering it with the already infused oil and leave again for a few weeks.
Hot Infused Oil – There are a few different approaches to the heating process. — > Add herbs and oil to a saucepan and heat gently for approx 3 hours. In order to avoid frying the plant material you may need to turn off the heat occasionally to keep the oil at a low enough temperature.
— > Add herbs and oil to a glass bowl and heat over a pan of simmering water for 3 hours. Make sure the bottom of the bowl does not touch the bowl and you may wish to occasionally top up the water so it doesn’t boil dry.
— > Add herbs and oil to a casserole dish, bring to heat on the stove then transfer to the oven set to a low heat for 3 hours. Some herbs contain more water than others and are best used dried. Other herbs such as St John’s Wort are more potent when fresh.
If you use fresh herbs make sure all plant material is completely immersed and that you have shaken out all air bubbles. Some herbs contain a lot of water and you may find a layer of water beneath the oil layer. If that is the case discard that water. The more water, the shorter the shelf life will be.