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A liquid foundation is a product designed to enhance skin color and provide a natural looking appearance that helps cover or even out skin imperfections and discoloration. Liquid foundations are an important part of most women’s daily routine with an estimated 106 million American women using foundations and concealers in 2018^(1).

The important distinction in formulating green liquid foundations and conventional types is the choice of ingredients. “Green” typically means no silicone, no petroleum sourced materials, no ethylene or propylene oxide based materials, and the use of biodegradable/sustainably produced ingredients. All materials should be natural and produced from natural renewable feedstocks.

There are two types of liquid foundation formulations that are currently popular– oil in water and water in oil–with the latter being the most common. Water in oil formulations are popular because when pigments are incorporated into the continuous oil phase, the emulsion skin feel is significantly less drying. Pigments also are easier to incorporate into the oil phase than water with less agglomeration and a more even coverage.

It’s a dramatic shift from the past when oil in water foundations dominated. This occurred mainly due to the development of superior silicone based polymeric emulsifiers and emollients, which made it much easier to stabilize water in oil emulsions.  This trend continues to the present with silicone-based emulsions being the most common foundations sold globally. The current natural trend is expected to increase the demand for non-silicone based formulations in the future.

The typical water in oil liquid foundation consists of:

• Water
• Humectants (1-10%). Humectants help increase the product application time. They can also help improve moisturization and the formulation freeze/thaw stability.
• Emulsion stabilizers/electrolytes (.5-3%). Emulsion stabilizers work by increasing the viscosity of the continuous phase. Electrolytes are also useful because they can help reduce the particle size of the dispersed phase and drive more emulsifier to the interface.
• Emulsifier (2-5%). Emulsifiers help reduce the interfacial tension between the oil and water phases, allowing the water to disperse into the oil. The best emulsifiers are high molecular weight polymeric ingredients, which are better at stabilizing the interface.
• Emollient/waxes (10-20%). Emollients are needed to reduce the skin-drying effect of the pigments and allow for better spreading during application. Waxes can act as emulsion stabilizers by thickening the oil phase.
• Coverage pigment (5-20%) can be coated for easier dispersion .The coverage pigment is normally the anatase or rutile form of titanium dioxide but zinc oxide is also used.
• Color pigments/Iron oxides (1-7%) can be coated for easier dispersion.
• Preservatives (.5-1.5%).
• Pigment dispersing agent (.5-1.5%) – They aren’t needed if using coated pigments.
• Sunscreens (optional). Typically, combinations of micronized titanium dioxide and zinc oxide are used in natural based formulations and dispersed in the oil phase.

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General guidelines: Formulating natural water in oil foundations

• Utilize the lowest level of emulsifier needed (blends of are generally preferred). Start with 5% and reduce if acceptable.
• Co-emulsifiers improve stability and reduce particle size. Adding a small amount of high HLB co-emulsifier can help reduce the level of homogenization needed.
• Add 0.5 – 1.0% electrolyte to water phase. Magnesium sulfate heptahydrate (1%) is typically used, but I prefer zinc sulfate since it can also reduce perseverative requirements.
• Keep internal water phase between 50-70% for better stability.
• Add waxes or thickeners to the continuous phase to improved stability, if needed.
• Normally, homogenize after emulsion is formed. Be careful about over-homogenizing. The particle size for stable emulsions is approximately one to four microns. More coarsely dispersed emulsions tend to separate.
• Typically, add water to the oil phase slowly.
• Avoid air entrapment because it can reduce stability.
• Test stability in the package you will be using. Some plastics can cause problems.
• Polyols can help freeze/thaw stability.

 Green recommendations

• Humectants: Use glycerin or naturally produced pentylene or butylene glycol.
• All natural emollients: Squalane or jojoba oil.
• Natural based emollients: Capric/Caprylic triglyceride and isoamyl laurate.
• Emulsion stabilizers: Silica, silica silylate, quaternium-18 bentonite, quaternium-90 sepiolite/montmorillonite.
• Emulsifers: Tri (polyglyceryl-3/lauryl) hydrogenated trilinoleate, polyglyceryl-2 dipolyhydroxystearate, polyglyceryl 4 diisostearate/ polyhydroxystearate/sebacate.
• Pigments: Most pigments currently used are considered natural. I generally recommend using coated/milled pigments for easier processing. Good natural based hydrophobic coatings include hydrogenated lecithin and sodium stearoyl glutamate.
• Dispersing agent: Polyhydroxystearic acid, polyglyceryl 6 polyricinoleate, or lecithin (when using non coated pigments).

References

1. U.S. population: Do you use foundation / concealer make-up? (2018). https://www.statista.com/statistics/275729/us-households-usage-of-foundation-and-concealer-make-up/.

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