With sudden spurts of early summer growth all around us, herbs are crying out for different ways to stay with us and be used. One way is to make an infused oil. They are simple to make and once prepared, you can go off and do other things while they infuse.
If you ask a North American how to make an infused oil, (or those who are influenced by their practice), they will describe the sun method of infusion. This is where you fill a glass jar with fresh herb (possibly wilted for several hours or days to reduce the water content), covering the herb with your oil of choice so the entire area of herb is covered and either leaving in the sunshine or another suitable warm place for six weeks or burying in hot sand/earth overnight or for several days.
The only drawback to this method is that if you leave any part of the herb exposed to the air, or if you seal the jar tightly so water vapour from the fresh plant material cannot evaporate, mould may form or the oil may become rancid so that at the end of the six weeks you have to throw everything away. You need to check the oil regularly to ensure everything is ok.
The only herb I infuse by the sun method is St John’s wort. I pick the flowers either daily or every few days, place them in a glass jar and cover them with sunflower oil. St John’s wort is a very delicate flower and needs a very light oil, such as sunflower oil. The jar is then placed, uncovered, in my kitchen window sill until the end of September, early October when I strain out the plant material and place the infused oil in a clean jar, seal and date.
The jar is left uncovered to ensure the water vapour from the flowers can evaporate. You can put a lid on as long as it isn’t sealed, but I have had problems with doing this. If you are worried that flies or other insects might contaminate your oil, you can cover it with a cotton/linen jug cover or a small piece of butter muslin/cheesecloth.
St John’s wort oil can be made cumulatively. If you only have a small amount of flowers, these can be placed in a jar and covered with oil, then a further harvest can be added to the jar on further occasions until the jar is full. The oil will start turning colour after 4-7 days, gradually changing colour from yellow to pale pink to deep crimson as the active constituents of the plants are released into the oil. It will also take on a distinctive aroma, which is unique to St John’s wort oil.
Double infused oils
European herbalists usually prefer to heat their herbs using the double infused method on a stove/cooker using the principles of a bain marie/water bath so the oil of choice does not come in to direct contact with the heat source.
The term, “double infused” means that you use the same amount of oil for two separate amounts of herb. This usually means dividing your herb harvest into two piles which you add to the oil at different times, the first amount being added at the beginning and the oil then being strained and the first portion removed at the end of the required time, then the strained oil is poured over the second portion which is subsequently heated.
If you are intending to use the infused oil as a massage oil or salve for children or frail elders, you may wish to undertake a single infusion for some highly aromatic herbs e.g. rosemary.
Double boiler double infusion classic method
4 oz fresh or dried herb
Enough sunflower oil to cover 2oz of leaves (around 8 fluid ounces)
Either a double saucepan or a stainless steel pot with a lid small enough to place inside another saucepan.
Place half of the herb inside the inner pan and cover with the oil. Replace the lid firmly and place inside the other saucepan which is about half filled with water. Heat the external saucepan so that the water gently boils. Do not let the pan boil dry! Boil for about 2 hours, then remove the inner pan and strain off the oil, squeezing the herb if you can to remove as much oil as possible. Place the rest of the herb inside the inner pan and pour over the oil from the first infusion. Replace the lid firmly and heat the oil in the outer pan for a further two hours. Strain the oil into a heated glass bottle or jar and cap with a screw top lid. If using fresh herb, let the infused oil sit for about three days to make sure any water content separates out. Decant oil. If water drops are left in the infused oil it will go off more quickly. Label the oil with the name and date that you made it.
The need to weigh and measure your quantities of herb and oil is entirely up to you.
Henriette Kress, the Finnish herbalist, makes all her St John’s wort oil by picking up to three inches of the top of each plant stalk i.e. flowers and stem, then infusing using a hot double infusion.
You can heat your oil in a cookpot/crockpot on the lowest setting. You then have the choice of altering the timings and maybe heating overnight for a concentrated single infusion, or for two extended lengths of time for a double infusion.
Remember that oil heats at a temperature higher than water and if you are using fresh plant material, the water vapour will evaporate and collect on the inside of the crockpot lid. Be very careful when removing the lid. Try to lift it up and away quickly so the water droplets do not fall into the hot oil. If this happens, the hot oil can splash and burn you. (I have done this, it’s painful!)
Fresh herbs or dry?
As with making tinctures, some people advocate using fresh herbs for infused oils and others prefer to dry them first. Christopher Hedley recommends always drying calendula petals before infusing in oil because the resin content of the herb is so high. Calendula is probably the only plant material I dry before making oils which means it is usually a winter activity since it can take several months to completely dry the flower heads!
Interestingly, when I brought back some rosemary from Spain and dried it before making an oil, the oil was incredibly pale with little colour or scent, so totally different from my normal fresh infused rosemary oil.
If you use fresh herbs, the oil will contain a certain amount of watery matter which can make the oil go bad if not removed before storage. Removal can be achieved by firstly noticing the globules of water at the very bottom of the infused oil when you are pouring the final straining and leaving it in the pan. The oil can then be left for up to three days to insure the oil and water layers have separated, then decanting the oil again before final storage.
I have had one occasion when making a double infused fresh rosemary oil in a cookpot, where the resulting infused oil came out as an emulsion and took several months before the oil and water levels separated.
The presence of an aqueous (water) component to an oil does expose it to the danger of botulism being present, since the organism lives in water. The botulin toxin is not destroyed by heat so, if it is present, it cannot be removed. The danger of botulism is rare. I have never heard of a case relating to an infused herbal oil in any country and if your oils are only used externally there should not be a problem. You may wish to make lip balm from oils prepared from dry herbs as the botulin cannot live without water.
The type of oil you use to prepare an infused herbal oil depends on your preference and the availability and cost of your preferred medium. Vegetable oils are the most popular medium. Sunflower, safflower, olive, almond, avocado, jojoba, coconut are only a few examples of what is available. You will need to decide what you want to use and what you are prepared to pay for it.
In ancient times, animal fats were the most widely available form of oil and these were used for infused oils as well as lighting. “Leaf tallow” from around the kidneys of an animal is the purest form of fat. It is easily absorbed through the skin and is gaining popularity amongst herbalists who wish to use organic, local, sustainable oils with respect. Beef, mutton, pork, emu and bear fat are all suitable. If carefully rendered and kept in a cool, dark environment, the infused oil can keep without unwanted scent or deterioration for up to a year or more.
Infused oils should be kept in a cool dark place. If stored correctly they should keep their efficacy for at least two years or more if they remain unopened. You can usually tell if an oil has gone rancid or has no usefulness by the smell/scent. If an oil loses its scent but does not smell unpleasant, it is probably best to discard and make some more.
Oils are slippery and may be difficult to rub in. You may find it easier to make the infused oil with an oil which is solid at room temperature such as cocoa butter or coconut oil, especially if you don’t want to use beeswax for any reason. Shea butter is another vegetable oil which is solid, but melts at body temperature.
You may need to use a combination of solid and liquid oils to ensure you get a suitable consistency. If you are using cocoa butter, the combination is 2/3:1/3 of cocoa butter to sunflower oil.
To make a simple salve, grate up some beeswax and add it to the hot infused oil, stirring continuously until it melts. (About 1oz beeswax to 8 fluid ozs of oil) Test on the back of a wooden spoon to see whether it is of a suitable consistency, then pour into small jars and seal. If you are not confident to do the spoon test, an easier way of checking is to drop a very small amount of oil plus melted wax into cold water in a small bowl or mug. The salve will immediately cool and you can rub it between your fingers to check the desired thickness.
The salve will thicken on cooling, usually from the bottom upwards if you pour into cold jars. It will usually be a paler colour than the original oil. St John’s wort salve is pink, comfrey salve pale green and dandelion salve pale yellow.
The whole aim of both infused oils and salves is to deliver a dose of herbal medicine through the body’s largest organ, the skin. To improve the transfer through the skin, some herbalists add extra contents such as lanolin or honey. If you decide to experiment with these substances you must ensure the recipient is not allergic to the addition and is not diabetic. Since honey is also water based, it may separate out from the oil if not sufficiently emulsified.
Essential oils can be added to salves to improve their keeping (Vitamin E can be used in the same way) or to add scent. Use the least number of drops possible per fluid ounce of salve and never more than 4. If your salve is going to a household where young children live or visit, do not include any essential oil.
I once gave a calendula lip salve scented with ylang ylang oil as a Christmas present to my boss. Her three year decided to use the lip balm herself and her whole face became puffy. I was mortified, because I had not thought there would be any danger of a child getting hold of the lip balm. Luckily my boss was not upset as the swelling went down the following day, but ever since then I’ve not used any essential oil in any of my salves. The scent of fresh honey from the locally sourced beeswax is enough fragrance for me.