Let's make an emulsion!
Almost every cream you use is an emulsion - a mixture of oils and water. You can buy an anhydrous cream (not containing water) and they are usually called balms or salves and they can be sold as single use bars.
According to Wikipedia an emulsion is 'a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation'. Water and oil don't mix - so how do you make an emulsion?🤔
You need an emulsifier - surfactant that has water-loving (hydrophilic) and oil-loving (lipophilic) properties. When emulsifier is used it combines water with oil and a stable emulsion is formed. There are two types of emulsion:
⚗️ oil-in-water emulsion (O/W) where water is a continuous phase (it basically means that there's more water than oil) and oil forms droplets (dispersed phase) which are dispersed in water
⚗️ water-in-oil emulsion (W/O) - there's more oil (continuous phase) than water and water droplets (dispersed phase) are suspended in oil
Emulsifier's molecules have one side which is attracted to water and the other attracted to oil - when combined at the right temperature (if you need to heat your phases), at the right percentage and with the right force (high shear, low shear) they will suspend the dispersed phase in the continuous phase and create an emulsion.
Usually when making an emulsion I like to add some vitamins, actives and essential oils. All of this substances are sensitive to heat - their most desirable properties will be destroyed if you heat them. If you are going to heat your phases you need to add all heat-sensitive ingredients at the cool down phase. You can find a detailed explanation about phases on our website
Some emulsifiers don't require heating - you need to check with the supplier how to use it. Most suppliers have all the info on their websites but if you're not sure you should always ask😊
Another factor you need to take into account while making an emulsion is the percentage of emulsifier. Again all this info should be on supplier's page but be prepared to experiment until you find the best percentage for your requirements.
Some emulsifiers work better when the oil phase is low (e.g. 5%) and some work better with higher oil phase (e.g. 25%). If you're making O/W emulsion the total percentage of the oil phase will always be lower than percentage of the water phase - what I'm trying to explain is that you need to be aware of how much oils you're using. If you use too little emulsifier your emulsion won't be stable and phases will separate.
Last but not least to consider when using an emulsifier is the speed (force) you need to use to break the oil phase in O/W emulsion or water phase in W/O emulsion into droplets dispersed in continuous phase. This might require using a high speed/shear or low speed/shear. All info should be on the manufacturer's website but the more you experiment the better you will understand the emulsifier and how it behaves.
I read not that long ago on one of the blogs that beeswax is an emulsifier. This is not true. Beeswax is not an emulsifier. It can act as a stabilizer of cold blended 'emulsions' but a physical one. Emulsification is a chemical process where new connections between molecules are made where beeswax physically can hold water and oil together but only when conditions are optimal. If temperature, light intensity or any other factor slightly changes the 'emulsion' made with beeswax will separate immediately. You can use beeswax along with emulsifier - it will certainly help with stabilizing, but if you want
a proper emulsion you need proper emulsifier😉
What can go into oil phase?
In oil phase you have oils, butters, waxes, emulsifiers and any oil soluble ingredients.
Some oils cannot be heated - all the vitamins and other active constituents could be damaged by high temperature. You can tell if certain oil is heat sensitive by looking at its iodine value. Iodine value is measured by adding iodine solution to lipid (it can be any oil, butter or wax) - the more unsaturated lipid the more iodine solution it will react with. Iodine solution measured in grams is added to 100g of oil or other lipid to determine its iodine value. If the oil has iodine value above 100 it is considered a heat sensitive. Anything below 100 could be heated.
What can go into water phase?
Here goes any hydrosol, floral water and glycerin plus other water soluble ingredients if they are not heat sensitive. There are also some emulsifiers that must me added to the water phase.
Cool down phase
Anything that is heat-sensitive goes into cool down phase: vitamins, active ingredients, heat-sensitive oils, extracts, preservatives and essential oils if you use them.
I know some of you don't like the word 'preservative' in the skincare. It is supposed to be natural, right? Without chemicals, right? Well, water is a chemical substance too and you drink it 🙃
You CANNOT store an emulsion without adding a preservative! If you're going to use it immediately then that's fine - don't add any. If you'd like to make more and put it in a nice jar you must add a preservative! The amount of preservative you use isn't huge anyway and there are more and more natural and skin-friendly preservatives on the market.
Preservatives are used to kill bacteria, mould, yeast and fungi. These microorganisms can develop in your cream because it contains water. Water = life (think bacteria here😅 ) so if you want to enjoy your emulsion longer you need to preserve it.
Once your emulsion is made you need to check the pH of it. Our skin has a naturally slightly acidic pH - between 4,5 and 5,5. You want your cream to have a similar pH to this of the skin.
I'll explain more about pH in the next post when we'll be making a simple emulsion.
Hope you enjoyed this quick chemistry lesson😆
Look for an ingredients list on our Facebook page soon!