Saturday, July 5, 2014

Weekend Wonderings: Adding essential oils in the heated phase?

In this post - Heating, holding, freezing, and thawing our oils - Lexi asks: It's summer so time to break out the insect repellents. I want to make my own insect repellent lotion based on essential oils (e.g. lavender, eucalyptus, citronella). My product is 8% essential oils. I know you said that we are not supposed to heat our essential oils but I only obtain a stable product if I heat (otherwise the oils "seep out"). Are my essential oils really that delicate that I can't heat and hold and 65C? Thanks for all the information you are sharing on this blog.

Before you make anything with an essential oil, please check the suggested usage rates. 8% of anything seems really high for a leave on product, so please check the usage for each oil and research how to combine them together.

It sounds like your aren't using enough emulsifier as you note the product is unstable. When you add more oils to a product - this includes fragrance and essential oils, as well as extracts - you need to compensate for said oils in the emulsifier. The oil phase of a product includes every oil soluble ingredient in the heated oil phase and the cool down phase.

If you are using Polawax in this recipe, adding 8% essential oils to the product means you need 2% more Polawax in your recipe. 2% might not sound like a lot, but it really is when it comes to emulsifiers. If you're out by 2%, you will likely experience a lotion fail, which is what you're seeing with the oils seeping out.

The aside: Polawax is used at 25% the oils phase. If you have 24% oils in the oil phase, you would use 6% Polawax (24 * 0.25 = 6). If you add 8% essential oils to the product, you would have 32% oils phase, and you would need to use 8% Polawax (24 + 8 = 32 * 0.25 = 8). For e-wax, add 1% more, so you'd need 9% e-wax. Ritamulse SCG can't be used for more than 25% oils at all. (For other emulsifiers, check the suggested usage rate.)

As a question, are you heating and holding at 65˚C? The suggested temperature is 70˚C to 80˚C.

As for essential oils being delicate - they are. They contain a lot of volatile ingredients that will evaporate when they are heated or poured into a heated product, so we use them at lower levels to avoid said evaporation. You can confirm this for yourself when you're making products. Heat some oil to 70˚C, then add the essential oils to the mix. In another container, put some room temperature oils and add the essential oils to the mix. Notice how much more fragrant the heated oil container is than the room temperature oil. This is because of the volatile ingredients that evaporate on contact with the heat.

Join me tomorrow for more fun formulating with stuff and things!


cmzaha said...

Is this supposed to be 6 oz instead of 6%? (If you have 24% oils in the oil phase, you would use 6% Polawax ) Sorry, my last post did not show my name so I started over, and hopefully it shows up this time

Susan Barclay-Nichols said...

Hi cmzaha. I'm not sure what you mean. I don't use ounces in my recipes - I'm Canadian, so we use the metric system, which is easier to use than Imperial - and my recipe is in percentages, so we would use % instead of ounces. Can you clarify what you mean?

Lexi said...

Hi Susan. Thanks for answering my question I realize from your answer that I did not explain myself properly so will attempt to correct that.

Regarding the use level of essential oils, I have seen several "natural" insect products being retailed with higher levels. Don't know the rules on your site so will not identify products by name but some contained 5 to 15%. One product contained 10% citronella in addition to peppermint, lemon grass, geranium. Also, essential oils at these levels have been reviewed in scientific documents, did not see any advise about not using them at high levels for repellent properties.

Regarding the emulsifiers I am using glyceryl monostearate and ceteareth-20. When I incorporate the essential oils in the heated oil phase I achieve an emulsion that remains stable for 3 months and counting. If I incorporate my 8% essential oils in the cooldown (using same amounts of emulsifiers as I would in the heated oil phase)separation occurs in less than 1 week.

If I am not supposed to heat my essential oils, what tips do you suggest for achieving a stable product? I don't believe that my emulsifying system is the issue as I have achieved stability. I should not have to adjust my levels of emulsifier if essentials are in the cooldown phase (can't ignore a whole 8%). Any tips would be welcomed.


Susan Barclay-Nichols said...

Hi Lexi. Your lotion recipe might be stable, but it isn't stable once you add the essential oils, which means you need to make a change. You have a few choices, as I see it.

1. You can leave out the essential oils and have a stable lotion.
2. You could modify the amount of emulsifier you're using.
3. You could modify the type of emulsifier you're using.
4. If you're using the HLB method, find out the HLB of the essential oils and re-calculate the amount of emulsifier you're using.
5. You could use a co-emulsifier.

Everything I have seen advises against using the essential oils in the heated phase, so I'll continue to advise against it.