Wednesday, March 23, 2011

Scientific soap making part III: essential oils vs.fragrance oils

As I prepare to teach a couple of soap making classes in the coming weeks, one of the topics I'll be covering is essential oils vs. fragrance oils and the pros and cons of each in cold process soap making.  My clear preference is essential oils because they're natural and have beneficial properties that fragrance oils don't have.  But first, let's clarify what the difference is between the two.

Essential oils are natural scents extracted from the leaves, bark, roots, flowers, and fruits of plants.  Fragrance oils are synthetic blends of the aromatic compounds found in essential oils and elsewhere. 

Is one preferable to the other?  Strictly in terms of cold process soap making, it's a toss-up.

Essential oils have an edge in that they have benefits beyond just scent.  Tea tree is a great example because its natural antiseptic, antibacterial, antifungal, and antiviral properties are well researched and documented.  Eucalyptus essential oil's value in relieving symptoms of respiratory infections can make it a beneficial additive in skin and bath products.  Many beneficial claims are made for other essential oils, although most are poorly researched and largely unproven.  Fragrance oils, however, have no such additional benefits. 

A field of Bulgarian lavender, considered by many to yield the highest quality lavender essential oil.
It's a toss-up between essential and fragrance oils in that both can be problematic to use in soap making. 

A problem with some essential oils is that the temperature at which their scent vaporizes (i.e., the flash point) is so low it won't survive ordinary cold process methods.  Eucalyptus, unfortunately, is a prime example.  With a flash point of around 110 degrees F, it can only be used in a soap that is prevented from heating up and going through gel phase, and preventing gel results in inferior soap texture and appearance.  The Lavender Oatmilk bars pictured below are a perfect example of a soap that did not go through a proper gel.


See the rind-like appearance of the outer edge?  It's noticeably lighter than the center of the bars, and it has a somewhat chalk-like texture.  Bars like these I either use myself or give away. 

Fragrance oils, on the other hand, have high flash points so that's not an issue.  The problem with fragrance oils is that some accelerate the saponification process and cause the soap batter to become so thick so quickly that it becomes difficult or impossible to pour.  With some I've used, the window of time between when the fragrance is added and when the soap becomes so thick it glops out of the pot rather than pours is less than 60 seconds.  You gotta be ready to move fast! 

Fragrance oils have an edge in cost and lifespan.  With just a few exceptions, fragrance oils are less expensive than essential oils.  Those with which I've been happiest cost around $1.50 per ounce, and their scents hold up for years, both in the bottle and in the soap.  Many of the more popular essential oils, on the other hand, average around $3.00 per ounce, and some (jasmine or sandalwood, for example) cost hundreds and even thousands of dollars per ounce.  Essential oil scents also tend to fade faster.  Citrus oils can be especially short-lived in soap, with noticeable scent degradation in as little as six months.

One thing I personally like about fragrance oils is that I can use or experiment with scents that are either too costly to buy as essential oils -- like jasmine and sandalwood -- or that aren't available as essential oils.  I do love the fresh, crisp, clean and slightly astringent scent of cucumbers, for example, but there's no such thing as cucumber essential oil.  You can also get fragrance oils that are imitations of popular designer perfume and cologne scents, which some folks really love.

An open question is whether one is safer for skin contact than the other.  Essential oils are derived from natural sources, but some are known to trigger adverse skin reactions.  Lemon essential oil, for example, is known to be irritating or sensitizing to some people's skin, as are spice essentials oils such as cinnamon and clove.  Synthetic fragrance oils . . . well we usually don't know how safe they are because the compounds used to make them do not have to be itemized on product labels.  We do know that phthalates used in fragrance oils and many plastic products have been linked to a number of health risks, but most fragrance oil manufacturers that used them have reformulated their products to be phthalate-free.

But whether scents are natural or synthetic, their effect and power is something I find endlessly fascinating.

I recently invited a friend to smell the scent blend I used in a new soap I formulated. She sniffed and appeared to have no reaction at all, just a funny kind of blank look on her face. 

 
"It reminds me of playing with Barbies," she finally said, completely unable to say why, or even whether that was a good thing or a bad thing.  The most she could add was that she didn't mean the soap smelled like a Barbie doll, just that it reminded her of playing with Barbies. 

Science can help to explain how we perceive and process scents, but it can't account for the uniquely personal associations we make with them or the emotions they trigger.  That is beyond both the art and the science of scent development.  And that is the reason I so enjoy experimenting with new scents and scent blends, using both natural and synthetic fragrances. 

One customer told me she absolutely loved a soap she bought that smelled like leaves burning in the fall.  I personally can't imagine wanting to use a soap that smells like anything that's burning, but I totally understand that she has her own special connection to that scent, and that's all that matters. 

22 comments:

  1. Do the benefits of Essential Oils survive the saponification process? And if they do, how much benefit do they serve in a wash on, wash off product? I am a soap maker (hobbyist) and I use only essential oils. I have never had these question answered before

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    1. In general, yes -- both good and bad. On the good side, for example, tea tree's antiseptic, anti-bacterial and anti-fungal benefits do surive the saponification process and result in a soap with those qualities. On the bad side, people who find certain essential oils sensitizing or irritating to their skin will find soap made with them sensitizing or irritating.

      But the answer also depends on which benefits you're referring to. Many essential oils are claimed to have benefits that are not supported by any scientific research -- often because such research has never been conducted. Part of the reason for this is that essential oils, like any natural product, can vary significantly from one sample to another depending on the country and climate in which the plants were grown, the composition of the soil in which they were planted, the weather during a particular growing season, the manner in which they were harvested or processed, and much more. So what may be true for one batch of a certain essential oil may not hold true for another.

      With that in mind plus the fact that, as you note, soap is used to clean and then rinsed off, I make a point of being careful not to claim any benefits for essential oils that I do not know to be proven and documented. With a few exceptions, I limit myself to describing only the scent with words like "fresh" or "refreshing" or "soothing."

      Hope this helps, and happy soaping!

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    2. Hi, If an essential oil is scientifically recognized to have therapeutical effects, do these effects survive to saponification? Does the chemical structure of essential oil change during saponification causing a modification to its original therapeutic properties?

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  2. Great question, but much too broad for me to be able to answer. The answer would depend on which essential oil you are asking about, which therapeutic benefits you are interested in, and which chemical components are most important in providing that therapeutic benefit. There is no blanket statement that I or anyone else can make about whether the therapeutic benefits of any essential oil will survive the saponification process.

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  3. Hi, Have you ever made soap with any plant / nut which has saponification qualities to saponifi the oils?

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    1. Hello, and thank you for your question, but I don't understand what you are asking. If I answer the question as I think you have asked it, plants or nuts do not have the saponification qualities to saponify oils. The only substances that have the qualities needed to saponify oils to make bar or liquid soaps are sodium hydroxide or potassium hydroxide. If you would like to try rephrasing your question, please do, and if I can answer it I certainly will!

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  4. Hi, I mean instead of 'sodium hydroxide ' have you tried 'Soapnut Tree' or 'Yucca' or 'Soap Nuts' in power form, which have saponification qualities.

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    1. Ah, thank you for the clarification. The answer is no, I have not used any of those. None of the things you are asking about have saponification qualities. That is, they cannot be used to convert oils or fats into soap. They are naturally saponified. So you can't use them to make soap, but you can use them as soap. Does that make sense?

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    2. Thank you. I am thinking of making soap but not so comfortable with the idea of using lye. I don't want to have caustic effect on my soap. I am not sure whether the people who have done youtube videos or online blogs on soap making, have given correct recipes. So, I thought of using above mentioned plants instead of lye. But thank you for answering my question. Happy soap making!

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    3. I wondered whether concern about using lye was somewhere behind your question. You are smart to be careful about the sources from which you get recipes. I recommend going to your local library and checking out a book or two on soap making to get a really good understanding of how soap is made. I'd especially recommend Anne L. Watson's "Smart Soapmaking" as an excellent resource for beginners. Happy soap making to you as well!

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  5. How long can one expect fragrance oil to hold up in cold process soap? I began cold process soap making about a year ago. It seems that many of my soaps have lost fragrance or the fragrances have changed from the original scent after about six to nine months. Is this to be expected? I generally use fragrance oils from reliable suppliers at up to 1 oz. per lb. of soap. After making probably 45 different soaps, only a very few have reliably maintained their fragrance. Some that have maintained fragrance patchouli (essential oil), spearmint (essential oil). I have tried placing each in their own plastic container with the fragrance oil soaked in a cotton ball, but, honestly, this made them all a little funky. I soap at about 110 degrees F and do not wrap my soaps up in blankets as some do. I realize each recipe produces different results and much of it is trial and error. My soaps are actually quite nice, lathery, bubbly, but the fragrances are a disappointment.

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    1. Hi, and thanks so much for your question. In general, 6-9 months is about the point at which many essential oil (EO) fragrances will begin to fade. Also in general, EOs with lower flash points (citrus EOs, for example) tend to fade faster than those with higher flash points. I use a non-porous plastic shrink wrap to package my soaps, and I've found that individually "sealing" them in this manner once they've cured, helps to extend the life of the fragrance up to and even past the 9-month point. With synthetic fragrance oils (FOs), however, the issue of scent longevity is strictly a matter of trial and error, aided perhaps by the comments or reviews of other customers -- if the website of the supplier from which you buy them allows customer reviews. In my case, the supplier from which I've purchased most FOs over the years was excellent in terms of consistent, dependable strength and longevity of its fragrances -- until that supplier began reformulating all its FOs to be phthalate-free. Since then, it's been hit-and-miss. So in short, certain EOs or FOs are going to fade faster than others no matter what you do, but my experience is that packaging scented soaps in a non-porous material after curing is complete will help to extend the life of the fragrance.

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  7. Hi I recently made a batch of white tea & ginger soap that turned out badly & I'm trying to find out which of the 2 caused the problem. I infused distilled water with white tea bags & some fresh sliced ginger and then used this water as a 100% exchange for regular distilled water. When I added the lye, it turned very dark & smelled awful. Do you think it was the ginger or the tea? I know you have to freeze milks when using them in soaping, would freezing have stopped this problem?
    Thanks for help
    jane

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  8. If your using essential oils or fragrance oils in liquid soap which is added after the cook and it not subjected to saponification, which last longer? And which one will have a residual scent loner on the skin?

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  9. Hi, Sherry -- I only use essential oils in liquid soap, but from my experience, the fragrance of both EOs and FOs will probably last in liquid soap the same as it will in any other use, whether that's cold or hot process soap making, melt-and-pour soap making, or candle making. So if it's a scent that's prone to fading over time -- such as grapefruit essential oil, for example -- it's going to do that no matter what you've used it in.
    With regard to residual scent on the skin, that's primarily a matter of how strong the scent is when your customer uses the product. As an example, I have used lavender and grapefruit EOs to give my body oil formula a pleasing scent when sniffed and when first applied to the skin. But 10 minutes later, the scent will have evaporated, and users won't have to worry about the scent of the body oil conflicting with any other scents they might prefer. Hope this helps.

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  10. By the way Sherry, neither EOs nor FOs saponify. (Carol Manning-Grant)

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  11. Hi there. I have a question about substituting fragrance oils for essential oils. My favorite "recipe" calls for essential oils, but I do have a couple of fragrance oils I'd like to try instead for a change. Do I substitute in exact amounts, eg: 2tsp EO for 2tsp FO? Thanks in advance.

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    1. The answer to that is not simple, as I said to Katrina below, because you have to know how the FO holds up in cold process soap to begin with. EOs tend to be pretty consistent no matter where you got them from, but FOs can be hugely variable from one supplier to another, and in one strength to another if the supplier offers varying concentrations. It's trial and error with FOs. See how it holds up first on its own, then try using more or less of it in a blend.

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  12. Would you use an equal amount of each fragrance or essential oils, if you were substituting one for the other?

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    1. Hi, Katrina -- The answer to that is not simple, because you have to know how either the EOs or the FOs hold up in cold process soap to begin with. EOs tend to be pretty consistent no matter where you got them from, but FOs can be hugely variable from one supplier to another, and in one strength to another if the supplier offers varying concentrations. It's trial and error with FOs. See how it holds up first on its own, then try using more or less of it in a blend.

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  13. Yes, Carol, that's absolutely true. I assumed that Sherry meant that the EOs or FOs would be subjected to the saponification process, as opposed to being saponified themselves. I hope I was correct in that!

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