Formulating for Success

In personal care, the product form and delivery systems go hand-in-hand in shaping the product experience and building brand recognition among consumers. A few innovations in this area have included foaming facial milk, sprays for skin protection and relief, and air-cushion foundations. The success of such products depends on the choice of key ingredients, as they dictate the stability of the product as well as the ability to deliver expected performance and consumer experience. 


Sprayable formulas have always been popular for sun care and body care products broadly applied to the skin. They are also popular for the fast-growing segment that addresses the demands of active lifestyles. Among such products, emulsion-based sprays are gaining popularity as they offer a special advantage of avoiding the skin irritation that a consumer may experience from ethanol-based products, or water-based, one-phase systems that are usually easier to make and more common in the market.  


Foams have traditionally been associated with rinse-off products, but nowadays they are appearing in leave-on applications such as foaming masks, mousse and foaming essence. Even in rinse-off applications, there is a noticeable growth in wash-off masks that foam while remaining on your skin before being washed off.


Since their introduction in recent years, air-cushion packages have been quickly adopted for use in color cosmetic products such as foundations, BB creams and CC creams. The sponge-and-puff combination in an air cushion may allow a more natural look with the use of a foundation because it can provide better distribution of the product on the skin, and noticeably reduce an uneven appearance. Therefore, air cushion packages are expanding the ways in which conventional liquid foundations can be used. They also fit the on-the-go lifestyles of consumers who want to carry a product for a touch-up during the day or before an evening event if they are not returning home.


Why They Are Popular


In applications such as sun care, high levels of organic or inorganic UV filters give products a heavy skin feel. This can be alleviated, to a certain extent, via spray form that provides a comparatively light skin feel and easy rub-in. A spray form may improve the efficacy of UV protection compared to a lotion by reaching areas that might otherwise be missed and achieving a more even distribution. However, spray delivery and coverage are critical for adequate sun protection. Sun sprays are also considered less messy and more convenient so they are easier for a person to reapply to themselves, to children or others. They also fit the on-the-go lifestyle of beach-goers and outdoor enthusiasts compared to other application forms, such as creams or lotions which take longer to apply. In addition, the spray form product may provide a feeling of refreshment during and after sport activities when skin temperature is elevated and there is a higher level of sweat and sebum on the skin.


In leave-on applications, sensory attributes of a product, how it feels during application, are often a purchase decision determinant. Compared to conventional creams and lotions, foam-based products deliver new consumer experiences with pleasing air-infused textures. Foams may also improve product performance through ease of spreadability and better skin coverage. In the special case of wash-off masks, some foaming bubble formulas claim to unclog pores and perform a deeper cleansing than common wash-off masks.


Air-cushion packaged foundations offer several benefits in addition to the positive consumer perceptions already surrounding such products. They exhibit a very light and refreshing skin feel. Even distribution of these lightweight makeups can cover imperfections and give a natural and effortless look. With air cushions, it is easy and convenient to reapply makeup several times a day, for a fresh look all day.


Formulating Properties and Challenges


Emulsion-based sprays are advantageous over one-phase formulas, such as ethanol-based, because both oil-soluble and water-soluble active ingredients can be incorporated in an emulsion. Moreover, emulsions can also help avoid the skin irritation issues associated with ethanol-based sprays. However, emulsion-based sprays are challenging to formulate.


They are difficult to stabilize due to their tendency to separate at the low viscosity levels required for sprays. They also require relatively fine droplets because spray performance is linked to the droplet-size distribution of the emulsion. Therefore, the formulation attributes considered most important for sprays are low viscosity, long-term stability and droplet-size distribution.


For foams, the choice of the secondary surfactant is critical to three attributes that can shape the product experience: 1) rapid foam generation, 2) achieving a creamy, dense-foam quality, and 3) the stability of the foam generated. With surfactants, mildness always comes into play, especially with leave-on applications such as wash-off masks that are supposed to remain on the face for a while. For such applications, the secondary surfactant itself must be mild. In addition, it can mitigate irritation efficiency from other (non-surfactant) ingredients to achieve formulations with overall mildness.


It is relatively more challenging to create a liquid foundation product to be used in air-cushion packaging. The use of a sponge requires the liquid foundation to have very low viscosity, no more than 6000mPas. In addition, the oil-water interface is especially fragile and difficult to stabilize in the presence of heavy loading of various additives, such as pigments, UV filters and actives that may compound the difficulty of creating a stable formula. Coated pigments may tend to thicken the formula due to the “bridging” effect that often occurs between coated pigment surfaces.


Required Ingredients


Brands that cater to consumer demands of convenience, performance and pleasing sensory attributes via innovative packaging and forms should create products in spray, foam or air-cushion forms. However, the challenges already described indicate that selection of the right ingredients is critical to success. A product that promises pleasing performance but fails to deliver on stability, for example, could damage a brand’s reputation.


The formulation examples that follow give basic guidance with starting ratios for achieving success with these forms. Of course, formulations must meet multiple goals simultaneously, from regulatory compliance to final product performance. Personal care ingredient suppliers typically offer starting formulas for specific types of hair and skin care products and can often recommend specific chemistry or tools to solve particular challenges. Evonik, for example, introduced a new tool, Sensory Kaleidoscope, for formulating skin care products with specific sensory properties.


Innovative product forms always present challenges, but overcoming them can inspire consumer excitement and new product categories.


For more information, visit www.evonik.com/personal-care


Sprayable Formulas
A combination of cetearyl glucoside (Tego Care CG 90) and Polyglyceryl-3 caprate (Tego Care PC 31) as a main and co-emulsifier, respectively, enables PEG-free, very low viscosity and very robust stability for a sprayable emulsion (see O/W pump spray). It is critical that the cetearyl glucoside used in the emulsifier is of high purity (over 90%) and the cetearyl alcohol has a relative low content (under 10%) in the emulsifier in order to achieve very low, sprayable viscosity in the formulation.


Polyglycerol-6 stearate and polyglyceryl-6 behenate (Tego Care PBS 6) is also an O/W emulsifier with formulation flexibility for incorporating high amounts of water-soluble UV filters, insect repellents, electrolyte and natural preservatives. It is especially suitable for formulating low-viscous systems such as lotions and sprays.

O/W Pump Spray

Ingredient:	%Wt.
Phase A
Tego Care CG 90 (Evonik) (Cetearyl glucoside)	1.00
Tegosoft PC 31 (Evonik) (Polyglyceryl-3 caprate)	0.50
Tegosoft DEC (Evonik) (Diethylhexyl carbonate)	4.00
Persea gratissima (avocado oil)	2.00
Tegosoft CT (Evonik) (Caprylic/capric triglyceride)	4.00
Phase B
Water	81.61
Tego Carbomer 341 ER (2% in water) (Evonik) (Acrylates/C10-30 alkyl acrylate crosspolymer)	4.00
Kelcogel CG-HA (CP Kelco) (gellan gum)	0.03
Glycerin	2.00
Phase C
Sodium chloride (10% in water)	0.16
Phase D
Euxyl PE 9010 (schülke) (Phenoxyethanol (and) ethylhexylglycerin)	0.70

Foaming Lotion
This O/W foaming lotion is based on the natural emulsifier (cetearyl glucoside), Tego Care CG 90. The low-viscous formula includes capryl/capramidopropyl betaine (Tego Betain 810), a mild surfactant which helps create a pleasant foam texture. Tego Betain 810 as a secondary surfactant by itself is non-irritating with a >400 L/D ratio tested on a Red Blood Cell test, so it can be transversally applied in rinse-off and leave-on applications. It also offers special foam boosting properties in formulation.

Ingredients:	%Wt.
Phase A
Tego Care CG 90 (Evonik) (Cetearyl glucoside)	1.00
Tegosoft PC 31 (Evonik) (Polyglyceryl-3 caprate)	0.50
Mineral Oil (30mPas)	5.00
Tegosoft TN (Evonik) (C-12-15 alkyl benzoate)	5.00
Phase B
Glycerin	2.00
Lauryl glucoside (50% active)	2.00
Kelcogel CG-HA (CP Kelco) (gellan gum)	0.03
Water	75.97
Phase C
Tego Betain 810 (Evonik) (Capryl/capramidopropyl betaine)	8.00
Phase D
Euxyl K (schülke) (Phenoxyethanol, methylparaben, butylparaben, ethylparaben, propylparaben, isobutylparaben)	0.50

Air-Cushion Formulas
The solution for liquid foundation by Polyglyceryl-4 diisostearate/polyhydroxystearate/sebacate (Isolan GPS), and Palmitamidopropyltrimonium chloride (Varisoft PATC) is designed to address both problems that are commonly encountered in creating formulas for air cushions—viscosity and stability.


Isolan GPS provides among the lowest achievable viscosity of a water-in-oil emulsion, and Varisoft PATC tackles the aggregation of the pigment particles and controls viscosity increase from that phenomena. In addition, a low viscosity oil phase with good wettability to pigments gives overall high stability of such liquid foundation, even in a containment like air cushion.


This low-viscosity foundation (p. 70), based on a 100% natural emulsifier (Polyglyceryl-4 diisostearate/polyhydroxystearate/sebacate) Isolan GPS, provides a very smooth and clear finish to the skin. This is possible due to the addition of the low-viscous emollient (Diethylhexyl carbonate) TegoSoft DEC.  

Ingredients:	%Wt.
Phase A
Isolan GPS (Evonik) (Polyglyceryl-4, diisostearate/polyhydroxystearate/sebacate)	2.70
Bentone 38V CG (Elementis Specialties) (Disteardimonium hectorite)	0.64
Alcohol, 95% (Sinopharm Chemical)	0.32
Mineral oil	3.34
Tegosoft DEC (Evonik) (diethyl carbonate)	9.70
DC Fluid 345 (Dow Corning) (Cyclopentasiloxane, cyclo hexasiloxane)	6.00
Dry-Flo Pure (AkzoNobel) (Aluminum starch octenylsuccinate)	1.00
Talc 46 AS (KS Pearl) (Talc/triethoxycaprylylsilane)	1.00
Phase B
TiO2 CR-50 AS (KS Pearl) (Titanium dioxide/triethoxycaprylylsilane)	7.20
Unipure Yellow LC182 AS-EM (Sensient) (CI 77492 iron oxides, triethyoxycaprylylsilane)	0.60
Unipure Red LC381 AS-EM (Sensient) (CI 77491, iron oxides, triethoxycaprylylsilane)	0.10
Unipure Black LC989 AS-EM (Sensient) (CI 77499, iron oxides, triethoxycaprylylsilane)	0.02
Tegosoft DEC (Evonik) (Diethylhexyl carbonate)	6.00
Phase C
Glycerin	15.00
Sodium chloride	1.00
Varisoft PATC (Evonik) (Palmitamidopropyltrimonium chloride)	1.00
Water	43.68
Euxyl PE 9010 (schülke) (Phenoxyethanol, ethylhexylglycerin)	0.70

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Brian Yang, Ph.D., is a senior scientist in the Personal Care business line  of Evonik Corporation. He joined Evonik in 2002, and brings more than 20 years of experience in personal care applications to his current post. He earned a Ph.D. in physical chemistry from Missouri University of Science and Technology, focusing on surfactant association structures.
More info: www.evonik.com/personal-care