Using Modern Soapmaking’s Essential Oil Calculator

Many people enjoy using essential oils to scent their handmade soaps. Knowing how to blend oils to create a lasting fragrance in soap is one part of the skillset you will need. For the second part — knowing how much of each essential oil you can safely use — there is a calculator. In this article, I will briefly address the art of perfumery as it applies to essential oils in soap. I will then conduct a step-by-step exploration of the Essential Oil Dilution Calculator and how to use it to keep your products both fragrant and safe.  

When deciding on a scent for your soap, it is important to consider that not all fragrances will last through the saponification process as well as others. Essential oils vary widely in their strength and in the amount that is safe for skin use. For example, citrus essential oils such as Sweet Orange, Lime, and Lemon are notorious for fading in soap, even when used in high quantities. In order to keep the citrus scent in a soap, it is necessary to blend this top note with a heart note and a base note to give it longevity. (Using 10x Orange essential oil gives somewhat more reliable scent in soap, but still requires anchoring with heart and base notes.) Mixing essential oils to create a tenacious blend, or soaking essential oils in powdered clay or botanicals, is called anchoring. There are a few methods that people use to anchor their scents, but the verdict is still out on just how effective other methods besides perfume blending are. The first involves adding clay to the essential oils and allowing the clay to soak up the scent before using in soap. In a similar manner, you can use cornstarch or arrowroot powder. Another way is to soak botanicals and additives such as colloidal oats in the essential oils before using. A third way is to make a hot process soap recipe, which will require about half as much essential oil overall because it will not be subject to the caustic environment of pre-saponification. Finally, you can try using benzoin powder to soak your fragrance, or use benzoin essential oil as part of your blend to hold the scent.  

To anchor the scent, you will need to blend your scent with complimentary scents, known as accords, in order to create a lasting fragrance. When you make a fragrance blend, the top notes are what you tend to notice first, and those tend to fade the quickest, leading into the heart notes, which tend to be more lasting. The base notes have the longest life span of all and often require only small amounts to make a big impact. These three categories of scent notes — Top Notes, Heart (or Middle) Notes, and Base Notes — make up your accord. Top notes include fruits, citruses and some florals. Lavender, Jasmine, Rose, Lemongrass and other florals and herbs are usually heart notes. Base notes are woody and earthy, such as Amber, Sandalwood, Patchouli and Vetiver.  You can find fragrance note pyramids easily on the internet that will classify your essential oils for you, if in doubt.   

So, how do you make a blend of essential oils? There are hundreds of suggestions for possible blends on the internet. Or simply choose a top note and a base note based on what you have, and enter into the Essential Oil Calculator to see a list of suggested essential oil blends. Use their suggestions or make up a blend of your own.  To test out your own essential oil blends, try the Drop Method. Choose a top note and a base note, at least. Heart note is optional. Simply add one drop of essential oil to a cotton bud and drop into a jar. Add another drop of your second oil in the same manner. Close the jar and allow to blend for a few moments, then smell the contents. If one oil needs to be more prominent, add another drop on another cotton bud. Continue in this manner until you have determined what proportions of each essential oil you need. Remember that one drop equals one part.  

Now let’s look at using the “Enter Your Own Blend” function of the Calculator. For instance, if you want to make a lemongrass soap using 100% lemongrass essential oil and no other oils, you would simply enter “lemongrass” from the essential oil drop-down box and type in “100” for the percentage. Now, suppose you want to make a blend of three parts geranium essential oil and one part patchouli essential oil. You would select “geranium” from the drop-down box and enter “75” as the percentage. Then you would go to the next line and choose “patchouli” essential oil and enter “25” as the percentage. The essential oil calculator will allow you to create a blend of up to four different essential oils. One good blend uses 75% Sweet Orange essential oil and 25% clove essential oil. This creates a lovely orange pomander kind of scent. Or try Orange and Ginger together, or Litsea Cubeba, Lemon, Lemongrass and a touch of Benzoin essential oils together for a bright, lemony fragrance that lasts.  

How do you figure out percentages of essential oils based on parts? First, divide the total number of parts by 100. (example: three parts geranium and one part each of patchouli, one part litsea, one part rosewood equals SIX PARTS total). In the example, six parts divided into 100 percent equals approximately 16.6. Therefore, each of the six parts is worth 16.6% of the total of 100%. With that information, multiply the 3 parts of geranium (16.6 * 3 = 79.8%) to get the total percentage of geranium oil in the formula. Then simply enter 16.6% for each of the three remaining oils. You may need to enter 16.7 for one of those oils to balance out the total to 100%.  

Remember when calculating your usage rates for soap to use the weight of the base oils in your soap recipe for the total weight. This calculator supports both grams and ounces, so use whichever is appropriate for you. Then hit the “calculate” button and there you go — a chart of usage rates for your essential oils, from light to strong. If a usage rate appears marked in RED, that usage rate is too high to be safe for skin use in soap. Choose a lighter usage rate to be safe.  

We have explored the basics of perfume making and methods of choosing your own blends, as well as how to anchor those blends in your soap. Using the Essential Oil Calculator to decide on a recipe and the “Enter Your Own Blend” page to calculate proportions will keep your soap well-scented and also safe to use. What blends do you plan to try? We would love to hear your comments!