Preserving Essential Oil Properties & Scent In Soap-making

Add a touch of luxury to your soaps by adding essential oils. But wait…before you add your favorite essential oil into your soap mixture, it’s essential to understand some fundamental soaping principles so that your soaps will retain not just the scent but also its therapeutic properties.


We know that lavender essential oil is known for its antimicrobial property. Does this property remain in the soap? Does its scent last long?


To scent your soaps and ensure therapeutic properties are still intact, we recommend that you make your soap using the melt-and-pour method with a soap base, via hot process (HP) method or liquid soap. You are basically adding essential oil when the alkali or lye in the soap mixture is no longer active.


Essential oils with high boiling points are the best choice for MP and HP soaps, while there is more freedom of choice for liquid soaps as the essential oils are added when the liquid soap is at room temperature.


What if you are making soap using the CP or cold process method?


When you make soap using the CP method, the lye is still active when you add essential oil unlike the hot process or melt-and-pour methods.


CP or cold process soaping is so named because no external heat is added during the process. When lye water is added to the oils during the soap-making process, the soap mixture saponifies.


In this process, the soap mixture releases heat to its surroundings in an exothermic reaction. The mixture can heat up to 93℃ or higher.


In fact, the addition of certain essential oils like thyme, clove, and cinnamon or even goat’s milk can increase the temperature of the soap mixture too!


The process of saponification and the resulting heat during soap-making will alter the oils. Some essential oils like bergamot, clary sage, lavender, petitgrain, thyme, and ylang-ylang are greatly affected by temperature changes. Naturally, the essential oils continue to evaporate during the soap-curing process too.


Citrus essential oils may not scent soaps as intensely because they evaporate more quickly compared to other essential oils. They are more likely to “disappear” in terms of scent. If you are unsure which essential oils can last longer in soaps in terms of scent, we will be happy to advise.


While scents do fade off during and after the soap-making process, it seems that their therapeutic properties do not disappear entirely when they are combined with lye. However, the proportions of the constituents in the essential oil will change as it reacts with lye.


Robert Tisserand, one of the world’s leading experts on aromatherapy and author of Essential Oil Safety notes “There is plenty of anecdotal evidence that essential oils in soap are active.”


The changes that occur during saponification “…may or may not result in an alteration of therapeutic properties. That depends on which properties you are measuring and also on which constituents you are talking about, so there isn’t a simple answer. Except perhaps to say that in MOST instances essential oils do in fact retain some of their therapeutic action!”


If you are using the CP method of soaping and wish to preserve as much of the essential oil scent as you can, try these tips:

  • Add a higher percentage of essential oil. (Check with us if you are unsure how much more to add to your soap!)
  • Mix essential oils with clays like kaolin clay, bentonite clay or cornstarch, or tapioca flour to anchor the scent
  • Blend your essential oil with another essential oil that has a base note classification such as patchouli, vetiver, ylang-ylang, myrrh, or sandalwood. The base note essential oil will help anchor the scent
  • Cure your soaps in an area that does not have direct sunlight
  • Wrap your soaps tightly after curing


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