This week I had a question from one of my online students about how to work out the safe limits for materials in the fragrances she is creating. There was a lot of confusion because every book she looked at written by different aromatherapists stated a different number of “safe drops” per ml of base oil. Then looking at IFRA it was a safe percentage of particular materials. I see this so much and people get into such a muddle so I want to clarify a few things here.
Firstly NEVER EVER use drops if you want an accurate formula, here’s why. Every liquid has a slightly different weight to volume ratio, so 1 drop of say bergamot oil will be a different weight and volume to say vetiver which is heavier and thicker. This means it is impossible to say how many drops is equal to 1ml or 1g and therefore impossible to work out a safe percentage in a finished product because it depends on the materials you use. Also what is the size of a drop? It depends on the dropper you use, the height you hold the bottle at, how hard you squeeze the pipette or how much comes out of the hole. Impossible to know what a drop is as packaging and people vary.
So forget drops and use a scale – preferably one that goes down to 0.01g and use percentages instead.
Many people who come to my classes say “I’m terrible at maths” (or math if they’re from the USA) and get embarrassed as they don’t know how to work out the percentage so if that’s you please don’t panic as I’m going to give you an easy way to work it out. If you struggle with this stuff then just stick to using units of 100 or 10.
So if you are making a fragrance at a strength of 20% and you are making 100g then 20g will be your fragrance concentrate and 80g will be your base (oil or alcohol). If you are making 10g then it will be 2g fragrance and 8g base. This makes it easy to scale up – 30g at 20% would be 6g fragrance and 24g base.
When you are formulating a finished product such as a cream or lotion or even a perfume oil or alcohol based spray we always need to make sure the formula adds up to 100 so we can scale it easily but this is not the case with a perfume concentrate. The concentrate is the creative perfume bit and often we want to add tiny amounts of materials and not be tied into getting the % correct so it adds up to 100. Of course we will need to know at some point that our formula is compliant and safe so I would recommend you create freely using a scale for accuracy and then check it using and excel spreadsheet afterwards rather than confusing yourself and stifling your creativity with the maths as you go. You can then check certain materials for safety on Good Scents and IFRA too.
I created a spreadsheet for my newsletter subscribers to help with this. If you’d like a copy just subscribe to my weekly newsletter HERE