I have been using essential oils for years without really knowing anything about them. I used them because I enjoyed the scent and occasionally for their magical properties when making incense. The only blends I ever attempted were from recipes in books, like Cunningham’s Complete Book of Incense, Oils, and Brews. Sometimes, the blends were beautiful. Others, not so much. Other than “these oils smell like crap together”, I didn’t understand why until I learned about blending factors while working through Simply Earth’s Essential Oil Heros course (which you can access for free with a subscription to their recipe box).
A blending factor is basically a scale from 1-10 that rates oils on the intensity of their scent. Using blending factors allows you to create blends where one oil doesn’t overpower the rest. You can find blending factor charts online, but I use the one provided in the Essential Oil Heros course (which I won’t upload for copyright reasons).
Recipes you find in books or online can often be improved by adjusting the amounts using the blending factors. As an example, I will use blending factors to adapt a recipe from Cunningham’s book.
Note: blending factors should be used to create a master blend, which should then be diluted for topical use. Do not simply top off the bottle with a carrier oil.
Love Oil (Original)
7 drops Palmarosa
5 drops Ylang-Ylang
1 drop Ginger
2 drops Rosemary
1 drop Cardamom
Palmarosa: 5 or 6
Ylang- Ylang: 4
Rosemary: 4 or 5
As you can see, the Ylang-Ylang, Ginger, Rosemary, and Cardamom should be used in roughly equal parts. In the original blend, the ylang-ylang and rosemary would be a bit overpowering. This particular recipe wasn’t too far off from the blending factors, but some of the recipes you will find online are in much more desperate need of improvement.
Once I have the blending factors for the ingredients, I like to make a sample blend using the factors are the number of drops. If an oil has a range, like palmarosa and rosemary, I go with the lower number first. Once I have my sample blend, I decide if I want to tweak it by increasing any of the oils that have a range, or just abandon it if I don’t care for it at all. In this case, I decided that it could use another drop of palmarosa, but the rosemary was just fine.
Now, I have my recipe and it’s time to do a little math to create my master blend. Add up the number of drops of each oil in the recipe. This is the total blending factor. In this case, I have 22 drops since I used 6 of the palmarosa. Now, divide the individual blending factors by the total blending factor. This will give the percent of each oil in the blend, expressed as a decimal. For small batches, like 5 or 10 ml, rounding to two decimal places is accurate enough. If you are making a large batch the rounding error will have more of an impact upon your final blend, so you’ll want to round out farther. Here’s the math for my recipe, rounded to two decimal places:
Palmarosa: 6/22 = 0.27
Ylang-Ylang: 4/22 = 0.18
Ginger: 4/22 = 0.18
Rosemary: 4/22 = 0.18
Cardamom: 4/22 = 0.18
The sum of these numbers should be very close to one. In my recipe, they add up to 0.99. I can either call this close enough or I can adjust one of the oils. If I were to adjust an oil, I would increase the rosemary to 0.19 because I chose to use blending factor 4 rather than 5.
Now that you have your numbers, you can make your master blend. I like to make 5 ml at a time. A milliliter of oil is roughly 20 drops, so we’ll be using 100 drops total. Some oils may be more or less than 20 drops depending on their viscosity, but this estimate will be close enough for a 5 ml batch. To figure out how many drops of each oil to use, multiply the decimal value by the total number of drops. For a 5 ml batch, I would multiply by 100, so my final recipe for a 5 ml batch is:
Palmarosa: 27 drops
Ylang-Ylang: 18 drops
Ginger: 18 drops
Rosemary: 19 drops
Cardamom: 18 drops
I hope this example was helpful. Please leave a comment if you would like any clarification.