- 1). If working with fresh rosemary, allow it to dry out in a warm, dark place for several hours. Make sure the herb has lost most of its moisture, otherwise the essential oil can become contaminated with mold and spoil.
- 2). Strip the leaves from the woody stalks of your dried rosemary.
- 3). If using a double-boiler, fill the bottom pot with water and add two to three ounces of rosemary leaves to the upper vessel. Cover with two cups of grapeseed oil. Simmer on low heat for three hours. If using a crockpot, combine the rosemary leaves with the grapeseed oil and heat on the lowest setting for three hours.
- 4). Strain the oil into a clean, sterilized glass jar. Seal and set aside in a cool, dark place.