Chop 1 cup of fresh or dried herb or plant material you want to extract. Place the chopped material in the Mason jar.
Pour the oil over the chopped plant material. Cover the material with at least an inch of oil, generally about 12 ounces of oil for this method of cold infusion.
Seal the jar tightly.
Set the jar in a warm place, preferably in direct sunlight. Shake the jar once or twice each day to mix the product in the oil. Let the jar sit for about two weeks.
Strain the contents of the jar through a fine sieve or cheesecloth. Pour the oil in a clean dry jar; a dark jar is best to preserve the extract. Store in the refrigerator.
Put 3 to 4 cups of chopped plant material in a medium saucepan. Add oil to cover the plant material.
Slowly raise the temperature of the oil until it is bubbling slowly but steadily. Don't allow the temperature to rise too high or the plant material will burn. Stir frequently.
Continue this low boil boil and stir for up to 4 hours or more. A minimum of 2 hours will give a weak extract, so stir longer for better results. When the herbs become crisp, they have transferred all of their moisture content to the oil and are completely extracted.
Strain the oil and plant material through a fine sieve or cheesecloth. Allow the oil to cool completely. Pour into dark-colored glass bottles and store in the refrigerator.