Lotion making is fun and easy once you get the hang of how it works. This is a brief overview of the things to keep in mind when creating lotions and creams.
Lotions and creams are emulsions - they are either water in oil (w/o) or oil in water (o/w). A w/o emulsion means you have small droplets of water dispersed in a medium of oil. A o/w emulsion means you have small droplets of oil dispersed in water. So the first 2 key ingredients of a lotion/cream are the oil and the water.
But as you know, oil and water do not like each other and therefore will separate if you don't have the 3rd key ingredient - an emulsifier. An emulsifier is an agent that helps bind the water and the oil together in a formula so it will not separate. Emulsifiers have different strengths or HLB values (hydrophilic lipophyllic balance) and therefore you need to choose your emulsifying agent carefully. Emulsifiers with low HLBs (3-7) are good for w/o creams or recipes that tend to separate slowly. A good example of a low HLB emulsifying agent would be a beeswax and borax combination. Higher HLB (10 - 18) emulsifiers are required when making o/w lotions. Emulsifying wax, liquid or solid soap and polysorbate 20 are examples of high HLB emulsifiers and are necessary when trying to make lotions or recipes that separate readily.
Creams Vs. Lotions
Creams are usually about 2/3 oil phase (oils, butters, waxes) and 1/3 water phase (all water soluble ingredients) while lotions are about 2/3 water phase and 1/3 oil phase. 5% beeswax is generally sufficient to give your emulsion body. These ratios can be adjusted according to your needs. The amount of emulsifier depends on what you are using but generally you will need about 5-10% if using an emulsifying wax or 15-20% if you are using polysorbate 20. Remember to add the preservatives to the correct phases before you combine phases. Water based preservatives should be stirred into the water phase and oil based preservatives should be stirred into the oil phase. The smaller phase should be added very slowly to the larger phase with constant mixing (mechanical mixing is recommended). The lotion/cream will change consistency somewhat as it cools so you may find that you need to adjust your recipe if it becomes thicker than you expected upon cooling.
Preserving Your Lotion
The last necessary components of your lotion or cream are the preservatives. Because your formulation contains both oil and water, you will need to protect both. Oils go rancid when they come in contact with oxygen and must be protected using an anti-oxidant. T50 vitamin E oil is a low alpha tocopherol suitable for this purpose. Rosemary oil extract is another. These can be used at .2- .5% and must be added to the oil phase. Water is susceptible to bacterial, fungal and yeast growth and must have an anti-microbial agent added to it. Paraben complexes and grapefruit seed extract are examples of anti-microbials. These should be added to the water phase at their recommended rates.
Chose your oils carefully according to the feel you want for your product. Heavy oils such as avocado and hemp are nice for winter creams but may be too oily for light formulas. Lighter oils are preferred for summer use such as grapeseed, apricot kernel, peach kernel, sweet almond etc. Fractionated coconut oil is both light and penetrating making it a good addition to any formulation. It will help carry other oils deep into the skin and prevent them from sitting on the skin. Using fractionated coconut oil will reduce the greasy feeling of most oils and butters.
Sometimes you will need to add a thickening agent to your lotions or creams to help attain the texture and spreadability you are looking for. Vegetable gums and starches are generally used to increase viscosity and improve the feel of the product. Look for easy to dissolve gums that do not require pH buffering. Xanthan gum can be used for this purpose.
Hydrolyzed silk can be used to provide a silky slip to your formulation. Modified starches (coming soon) can be used at 1-5% to reduce the heavy greasy feeling of the oils and waxes.
Generally, the first step in the process involves heating the oil phase - the waxes and solid fats. The water phase should be warmed too and both phases should be equal in temperature when the phases are combined.
Coloring and Fragrancing
Creams and lotions are easily colored with the use of liquid FD & C dyes as they readily mix with water. Insoluble colorants are not a good choice for lotions as they tend to settle to the bottom. Scent your lotions and creams once they have cooled slightly by stirring in your fragrance or essential oils.
Finally, make sure that all of your equipment is clean and sterilized. Use glass and stainless steel for mixing. Bottles can be sterilized ahead of time using a solution of water and alcohol or water and bleach. Use only distilled water not tap water. Avoid touching the batch with your hands during transfer.