As with all herbal preparations there are always different methods you can use for the desired results. Here are the two main ways to make an herbal infused oil.
Solar Infused Herbal Oil
This is also referred to as a cold infusion and is made just like a tincture only we will use oil as our menstrum. Choose herb(s) of choice, chop finely and fill the jar to 3/4 full. Pour a high quality oil over the herb(s) to cover by 1-2 inches. Olive oil is my favorite oil of choice because it has a longer shelf life and has many medicinal qualities in and of itself, I also like the way it sets up in a salve. Grape seed oil is not as heavy so it works better for a massage or bath oil, experiment and find what you like best. If using fresh herbs make sure to dry wilt them first (let them sit for 4-8 hours to remove some of the moisture) use a coffee filter or cheese cloth to cover, secure with canning jar ring or elastic - we don't want any mold growing in your herbal infusion. Or you can just use the hot extract method which works best for fresh herbs. If the herbs are dry go ahead and place a lid on the jar. Place in a warm, sunny area for 2 weeks, shaking daily. At the end of the two weeks you can strain the herbs and do one of two things. For a more potent oil place a fresh batch of herbs into a jar and pour the strained oil over them, place in your sunny spot and infuse for another 2 weeks. This is called a double infusion. Strain and add 10-15 drops of rosemary or benzoin essential oil and shake or stir thoroughly, this acts as a preservative to prolong the shelf life of your oil. Store in a glass container with a label of the herbs you infused and the oil used. Store in a cool, dark location where your oil should last from several months to a year. When the oil loses its color and starts to smell "not right", you know it's gone bad.
Hot Infused Herbal Oil
Also known as a hot oil extract. There are two ways to accomplish a hot infused oil. This method allows you to have your oil ready within a day rather than waiting the two weeks and is the best method for fresh herbs. I prefer the solar infusion method during the summer months and the hot extract during the winter. The first way to do this is preparing your oil as above and placing the jar in a crockpot or pan of water with a towel or rag on the bottom to prevent your jar from breaking (don't look at my picture though, I am naughty and sometimes forget to use the towel). The water should go up to where the herbal infusion starts or to just below your lid. Bring the water to a soft simmer on low heat and let the oil sit in the simmer water for a minimum of 4-5 hours and up to 72 hours, shaking gently every once in a while and keeping the water filled. I keep my crockpot on the low setting.
You can also use a double boiler. Place the herbs and oil in the top part of the boiler. Slowly bring the oil to a very low simmer, you want the temperature to be between 95 and 110 degrees. Simmer for 30-60 minutes, making sure the oil is not overheating. The oil should turn the color of the herbs and smell potent. Strain the herbs and bottle the oil as above.