A solubilizer is a mixture of ingredients that allows a small amount of ‘hydrophobic’ (insoluble in water) ingredients to be uniformly dispersed in water or water-based products. Solubilizers belong to the surfactant group alongside emulsifiers. Although solubilizers and emulsifiers both belong to surfactants, solubilizers are more water-soluble than emulsifiers. A solubilizer works to disperse various concentrations of oils in aqueous mediums. An emulsifier helps two immiscible ingredients blend to make a W/O or O/W emulsion.
If you want to add a small amount of oil, for example, an essential oil or fragrance oil, to a water base, you will need a solubilizer to blend the oil into the water base. A classic example is a facial toner with essential oil. Without a solubilizer, any essential oil added to hydrosol, in this instance will have oil droplets floating on the top of the water, as oil and water do not mix well.
Many DIY home-crafters find it unnecessary to use any solubilizer. And you can notice this by looking at their finished product. There is a layer of oil droplets floating on the top of the clear liquid. If no solubilizer is used, you will need to shake the bottle before application. This may cause a safety issue, in which each application of the product may be different. This can cause sensitization and unwanted reactions if essential oil used is exceeded the dermal limit. In a uniformly solubilized product, the essential oil and the preservative are evenly dispersed in the product. Thus the whole product concentration will be the same, and importantly, the product performs better as the essential oil is dispersed as tiny (nanometer) invisible droplets.
Using solubilizer will create the overall finished product to have a clear and transparent appearance.
Essential oil (EO) should be tested for each EO blend individually to reach the optimum ratio of EO : solubilizer.
Not all essential oils will need exact ratios, and it widely varies for different essential oils. It can even vary for the same essential oil from different suppliers or different harvests. It is important to do some initial tests if you plan to make a huge batch of your product. The amount of solubilizer required will depend on the polarity of the oils to be solubilized. The more polar the oils, the less solubilizer is needed.
Steps to Find the Golden Ratio of EO : solubilizer
1. Start small batch tests, blend the solubilizer and EO, mix until homogenous. Add distilled water to the mixture to find out the least concentration of the solubilizer that can solubilize the essential oil in plain distilled water.
2. There is no need to test the solubilizer with a ratio for instead 5% of an EO if you plan to use 0.5% in the formula. Consider the concentration and work with that concentration to find the ratio of the EO blend in the final product
3. The combination depends on the type of the essential oil you are using, and it varies from EO : solubilizer ratio 1:4 to 1:10 (Please always check the supplier’s guide for the ratio)
4. Start with a 1:4 ratio and observe the blend. It may take a few hours for the mixture to become completely transparent/transluscent.
5. If the solution appears transparent after 24 hours, slightly reduce the concentration of solubilizer to see if that work. If the solution does not become transparent, increasing the solubilizer dosage to find the most suitable ratio. Repeat the experiments until you find a concentration that works.
After finding the most suitable ratio of EO : solubilizer, you may blend the EO with solubilizer of this golden ratio before adding it to the base product.
If your preservative has oil-soluble components such as benzyl alcohol, you will need to blend the preservative in the essential oil with solubilizer as well.
Assign percentage (%) in your formula for the solubilizer and reduce the water accordingly.
Look at how below example on how the formula changes when adding essential oils and a solubilizer to a base toner formulation:
This 1-page printable chart is perfect for essential oil users as it shows the families used in perfumery by aromatherapists, depending on their botanical origin.
This 1-page printable is on the best practices for essential oils. To confidently use essential oils, there are several safety precautions you need to be aware. This guide is great as a quick and easy reference
This 1-page printable chart is perfect for essential oil users as it covers the basic applications with recommendations to help you choose which oils you want to try in customizing your skin-care products.
The most widely available and used solubilizers so far are polysorbates (specially polysorbate 20) and PEG-40 hydrogenated castor oil. They both work excellently, are very easy to work and forgiving ingredients. However, because both of them are PEG-derivatives, so they are not considered “natural” cosmetics but general they are much better than “natural” solubilisers.
INCI: Caprylyl/Capryl Glucoside; Aqua; Sodium Cocoyl Glutamate; Glyceryl Caprylate; Citric Acid; Polyglyceryl-6 Oleate; Sodium Surfactin.
Recommended usage: 1:3-1:5 (oil:solubilizer) ratio.
INCI: Polyglyceryl-6 Caprylate (and) Polyglyceryl-3 Cocoate (and) Polyglyceryl-4 Caprate (and) Polyglyceryl-6 Ricinoleate
Recommended usage: up to 10%.
When using this solubilizer, you should follow percentages rather than ratios. The maximum usage is 10% in a product, so it is best if you work backward when designing your formula. For example, if you allocate 5% solubilizer in your formula, see how much oil that can handle and remain a clear blend.
INCI: Caprylyl/Capryl Glucoside
Recommends usage: up to 40%
All solubilizers are “surfactants,” they foam more or less. Capryly/Capryl/Glucoside is sold as a foaming agent and foam stabilizer and foams more compared to the other two. Due to its active solubilizing agent for essential oils and fragrances as well as a cationic surfactant, Caprylyl/Capryl Glucoside is an excellent choice for the formulation of foaming aromatherapy products.