Friday 6 May 2011

Revising the basics: Infused oils

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.

Sun Infusion
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.

Cookpot/crockpot method
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.

Which oil?
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
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.


Rowan said...

This is a really interesting and informative post Sarah. I'm going to print it off and have a go at one or two infused oils this summer. I have a small amount of St John's wort in the garden so will try that - hopefully if I keep picking the flowers it will keep producing more.
Still hoping to get down to a workshop during the summer/autumn.

Sarah Head said...

We'd love to see you again, Rowan. Let me know how you get on with the oils.

Lisa said...

After I have infused oil with flowers, can the remaining flower heads be used for anything? I'm thinking maybe they would work in homemade candles or even incense, although I've never made either (yet!). Any suggestions? Thanks!

Sarah Head said...

Hi Lisa, I don't think it would be a good idea to use flowers which have been infused in oil for anything other than compost after you have cooked them for two hours or six weeks if you are doing a cold infusion. For candles, you need fresh or dried flowers you attach onto the outside of your homemade candle with melted wax and for insense you use dried aromatic flowers which are crushed to release their fragrance and then fixed with an aromatic fixative like orris root. Flowers used to make oil are scentless and very, very soggy. When you have made your own oils, you will understand why I say this. Let me know if you need any help.

Anonymous said...

When making a double infusion, do you need to fill up the jar with extra oil or is the oil left after the first infusion enough?

Sarah Head said...

When you're making a double heated infusion, you don't use a jar, you either use the top of a double saucepan or a closed container in a bain marie or slow cooker. If you have halved your original amount of herbal matter and squeezed it out well when you strain it after the first two hours, the same amount of oil will easily cover the second half of fresh material. If you top up the amount of oil after the first infusion you will dilute the strength of the finished infused oil.

Paula said...

Hello, I have a question about oil going rancid. I made a batch of fresh rosemary & lemongrass infused in coconut oil. I used a crockpot. I tried to keep the temp. between 100-120, but it did get up to 130-140 for several hours. I kept the lid either off or half way on. By end of the second day the oil didn't smell right. Could it have gone bad so soon? Any suggestions? Also, I've read not to let the oil get above 120. Do you know why? Maybe that is my problem. Thanks!

Sarah Head said...

Hi Paula. There can be problems if you use a slow cooker to heat infusing oil directly as it can get too hot. It sounds as this has happened with your coconut oil. I'm not familiar with using this kind of oil but all oils have their own boiling/burning point when they become denatured and start to smell strange/off. It's probably better to make your slow cooker into a bain marie/water bath by putting the oil and herbs into a plastic or stainless steel container with a closely fitting lid. Place this in the slow cooker (on top of an old saucer if using a plastic pudding basin) then add one or two kettle fulls of boiling water so the water level is 2/3 way (max)up the side of the container. This way, the oil shouldn't overheat and there shouldn't be a problem with infusing your herbs. I hope you have better luck next time.

Lisa H said...

My infused oil smells rotten. First time this has happened. I'm guessing it's not good for use? What could be the culprit? Thanks in advance..

Sarah Head said...

Lisa, what were you infusing and how were you doing it? If you were using the sun method with fresh plant material and didn't fully submerge the plant matter, it may well have oxidised and decomposed hence the smell. It could also be the actual smell of the plant but until I have more details, I can't comment.

Lisa H said...

I apologize for being so vague. I was infusing Calendula flowers, sun method. I covered them an inch over with Olive Oil and mixed it by stirring it up every day. It seemed as though it was ok until the wek I wanted to strain it. When I took the lid off it smelled horrible...rotten almost. I haven't had it happen before but have 2 jars infusing right now and am being careful to not cap so tight.

Sarah Head said...

Lisa, I guess if you live in a very hot part of the world, using the sun method for fresh calendula flowers is ok. Personally I never use the sun method for calendula - they have too much resin in them and really need to be dried before you infuse them. I always double infuse dried flowers or just petals if I'm making the oil for myself. If I'm demonstrating at the farm and only have access to fresh flowers then I will double infuse fresh and get good results but I always warn people about the water and resin content. To be honest, I don't trust sun infusion for any herb except for St John's wort flowers which stay, uncovered, on my kitchen window sill for three months. The window is south facing and gets very hot every day the summer sun shines. The one time I put a lid partially on, mold grew so I've always left it open since.

Lisa H said...

Thank you Sarah, I appreciate your help! I'm definitely chalking it up and looking forward to the next batch. God bless, Lisa

Lauren said...

Hi Sarah, I just attempted to make a cottonwood bud infusion in olive oil. After two weeks the oil looks cloudy and the smell is very strange (like very strong green olives, maybe this is normal?). The oil bubbled dramatically when I opened the jar. The buds were freshly harvested. I covered the top of the jar with a paper towel to allow for water evaporation during the first week - maybe this was not long enough. It seems off and I'm trying to learn from this experience!!! Any ideas where I went wrong? Do you make cottonwood bud infusions? If so is there a method you use or like over others? Thanks so much!

Sarah Head said...

Hi Lauren, It sounds from your description as if your infused oil is somehow fermenting. Cottonwood doesn't grow in the UK so I've not made any personally. I would recommend you you make a double infused oil by the heating method, don't do a lengthy sun infusion. Cottonwood buds, like balm of gilead/balsam poplar buds are full of resin so either need to be heated during infusion with oil or dried beforehand like calendula and then heated. I'm afraid you'll need to gather some more and try again. You can save what you have and use it for woodworking or something else but I'd be wary of using it medicinally.

Lauren said...

Thank you Sarah! It has been difficult to find advice on this subject. I will start a double infusion today!

Gunhild Johnson said...

Hi Sarah!

I just tried making a calendula maceration and failed. The oil smells off now only after a week. I wilted them first, broke them up (but clearly not enough) and checked every day and stirred to remove air bubbles etc. I left it uncovered only part of the time. How do you know if the oil has gone bad, and what do you do with it if it has gone bad? Thanks in advance, and thanks for the great post :)

Sarah Head said...

Hi Gunhild, If you're making an infused oil from fresh calendula than it may well smell off because of the resin in the plant material. I don't make cold, macerated herbal oils - there is too much which can go wrong and you lose your entire product. I always dry my calendula heads first, which means either using a dehydrator or leaving them in a paper bag for several months in a warm place. You always need to make sure the plant heads are completely dry when you pick them, so if you live in a humid environment you may be in trouble. I have made calendula oil from fresh plant heads using the double boiler double infused method. The oil has a lovely colour but it's not as concentrated as the oil made from dried petals.

With your current oil. You could try heating it in a double boiler for a couple of hours and see if the smell disappears once the plant material has been strained off. Otherwise I'm afraid you'll need to discard everything and start again.

Unknown said...

Help! I got so excited after hearing a friend talk about herb infused olive oil, I went out to my garden and went right to it without researching the steps to properly infusing oi. I currently have a mason jar filled with olive oil and herbs in my fridge, its been 3 days. I watered my plants, picked a few sprigs of rosemary, set them at the bottom of my mason jar and filled it up with olive oil. Today i was doing some reaearch and discovered i did it wrong and could result in mold or rancid oil. I would really hate to throw the whole thing out, but dont want to consume mold. I guess my question is if my oil is still good to use if i see no visible signs of mold.

Sarah Head said...

If you only put a few sprigs of rosemary into your oil, you are only going to get a very mildly flavoured olive oil which could be consumed in a salad dressing. After three days nothing in a fridge nothing much will have happened. Next time fill your jar to the top with chopped up herb before filling with oil then either heat in a water bath or in the sun as appropriate.

Anonymous said...

Hello, just came across this webpage by random chance and enjoyed reading. Although opinions are not always welcomed unless entreated, I did - at the risk of sounding rude - want to add a note about using Vitamin E oil as a preservative. This is nothing more than common urban rumour and I do not know how it got started. Vitamin E oil has no worthy preservation powers and certainly in no way will it adequately stop bacterial activity from forming in oil-to-water blends.

Vitamin E has it's own special place in the pantheon of healing, but should never be solely relied upon to preserve (i.e disinfect) topical skin formulas that contain any percentage of H20. We would not want to place our loved ones or customers in danger. Please be careful when formulating and do plenty of research. A quick conversation with a Chemist, would be the ideal way to go, for starters.

Thank you.

Unknown said...

Hi there! I just came across this and I am curious as to why I would have to "double infuse." Can't I mix all of my dried herbs of choice and infuse into an oil over a double boiler? Why would I have to infuse one herb at a time in the oil? Thank you!

Sarah Head said...

Hi Samantha, if you only want to make a single oil and know exactly what herbs you want to put in it, you could add them all together. I do this sometimes if I'm making a fresh herb infused oil during a workshop. If you only infuse the oil once, it isn't as strong as infusing it twice, which is the strength most herbalists use. Also, you may want to make an oil with a different combination of herbs. It is much easier to make a combined salve using oils made from a single herb than it is with an oil which is already infused with multiple herbs. There may be a herb which someone is allergic to or a herb which isn't needed in the combination you are planning. I make single herb oils, tinctures and vinegars. The only extraction where I add multiple herbs is to an elixir when I'm making an "uplifting" combination which involves strolling around my garden picking all my nervines. Hope that helps.

Unknown said...

Hi there! I have been infusing different dried herbs in sunflower oil for some weeks and I noticed 2 days ago that the scent as changed,not strong like before it seems like it was giving off it's fermenting or so. This smell isn't unpleasant tho. What do you know could have happened or what do you suggest I do? Cheers!

Paula said...

I just strained my calendula/olive oil infusion. It was in a dim, not always cool spot (my house gets up to 80 degrees sometimes, made with dried flowers. I also made primrose oil that I haven't yet strained. My question is, they smell very strongly of olives. Is this okay? It doesn't look weird, I just wasn't expecting this smell. Could it be going rancid? I plan on using it's my first time and I'm just not sure if it's okay.

Thank you

Sarah Head said...

Hi Paula,
Neither dried calendula nor dried primrose have a strong smell, so the scent of the olive oil will always predominate. Infusing herbs in oil always requires heat, either from the sun, hot sand or in a bain marie/slow cooker or double saucepan above heated water. When an infused oil goes "off" you can always tell from the smell. I would describe it as "reesty" but that's a family term so I'm not sure how widespread it is. If your oil only smells of olives, it should be fine. Store it in a wide mouth jar with a lid and keep it sealed so it doesn't oxidise. If you keep it in a bottle, there is the likelihood that the oil droplets on the sides of the bottle neck will oxidise quickly and affect the rest of the oil. Olive oil is absorbed quite well by the skin but you may want to use a small amount in a salve as it is easier to apply when thickened rather than just an oil. Good luck!