Infused herbal oils are lovely. Often you get subtle but distinct scents to them, and they can be used for medicine and/or cosmetics.
Here’s how I made arnica oil yesterday.
Prepare your jar first. You want it clean and very dry. I wash a bunch of jars and then put them in the oven on a low temp for half an hour to get all moisture out of them. Moisture and oil and plant material usually equates to mould. Let the jar cool before making oil as hot glass and plant material also equals moisture which equals mould.
Pick the herb. Pick on a dry day where there has been no rain at all for at least 24 hours. Pick later in the day if there has been dew. Plants have some moisture in them, but moisture on the outside invariably leads to mould in the oil.
Chop the herb. Not entirely essential, depending on the herb, but I like to because it opens the plant to the oil, and because you get more plant into the jar therefore the oil is a bit stronger. I usually chop roughly, occasionally I chop finely or use a blender.
Fill the jar twice. Once with the herb, and then again with oil. I use olive oil because it is very stable and it’s good for the skin. Once the oil is in, use a chop stick or something to poke the plant to get as much air out as possible.
Cap and label. Put a lid on to keep out bugs. And label jar with date, plant and plant part, place of harvest, and type of oil.
Check the next day. Open it up to have a look, add more oil (usually the level has dropped because air has surfaced). The plant material must be cover in oil (or it will go mouldy).
Infuse 6 weeks. In a cool place out of direct sun (heat equals mould). That’s the length of time I was taught and I like it. The long time allows the plant to be extracted into the oil. Keep an eye on it, wiping any moisture from inside the lid and topping up oil as necessary.
Decant. I strain through a sieve, and then squeeze out in a cloth to get as much oil out of the plant as possible. You can let the decanted oil sit in a jar for a few days to see if any water settles on the bottom and then pour the oil off into a clean, dry bottle. Dark glass will keep the oil longer. Store in a cool, dark place.
Use and enjoy!