To help formulators create products that meet both product efficacy and sensorial needs, Cognis Care Chemicals has developed a model that allows precise customization of the texture of skin care products
As daily life becomes increasingly stressful, consumers are looking for new ways of unwinding. As a result, they are demanding cosmetic products that in addition to delivering the benefits they promise will also give them a sense of well-being and stimulate the senses including sight, smell, sound and touch. If products are to achieve this, the right texture is vital. The challenge for cosmetic formulators is to incorporate both an encompassing experience, including a highly appealing sensorial feeling, and cosmetic benefits into the same product.
One current trend is Nutri-Cosmetics - products such as lemon scented gel creams, honey scented soaps and yogurt scented lotions. The underlying idea is to leverage marketing claims and product experience from food products to cosmetics. But consumers don’t expect these products merely to smell like the food in question; their texture and appearance must also call it to mind. Thus it is no longer enough to just claim on the packaging that a cosmetic product is like yogurt . If nutritive care products are to succeed they must combine a pleasant, gentle texture with scents that consumers know and like from food products, offering a holistic sensory experience.
The direct impression a consumer gets from a skin care product is largely influenced by its texture. To achieve the right texture, formulators must have a thorough understanding of emulsion technology and how this is best applied. Texture is characterized on the one hand by the visual properties (eg white and shiny, sprayable, fluid, creamy, thick) and rheological properties (eg from pick-up to the feeling during application) of the emulsion, and on the other by the skin feel during and after application (eg smoothness, softness, stickiness). In order to obtain the correct feel and viscosity the formulator must find the correct combination of emulsifiers, consistency factors, emollients and other cosmetic ingredients.
To help manufacturers define the right texture for each product, depending on its intended purpose, a new two-dimensional model has been developed. The key is to find the right balance between sensory parameters, such as whether a product feels rich and gentle or fresh and light, and physical parameters, such as low, middle or high consistency and viscosity (Figure 1). This helpful model makes it faster and easier to develop formulations that support specific market positioning strategies. The model also facilitates the creation of novel textures for products developed in response to emerging market trends.
Customized textures
The most important types of o/w formulations are sprays, gels, creams and lotions. Sprays and gels in particular are becoming increasingly popular with consumers, with sprayable emulsions also being used to impregnate wipes. The model makes it easy to differentiate these products and give them specific characteristics.
Sprays Sprays have a low viscosity and a light/fresh skin feel while delivering moisturisation and care. This texture can be achieved by:
• Using phase inversion technology based on ethoxylate containing emulsifiers (ceteareth-20, ceteareth-12)
• Making sprayable emulsions based on ethoxylate-free emulsifiers (lauryl glucoside, polyglyceryl-2 dipolyhydroxystearate, glycerine) which are then stabilized with polymeric thickeners
• Using strongly shear-sensitive thickeners such as sodium magnesium silicate. When subjected to shear stresses, this type of thickener drastically decreases the viscosity of an emulsion, which means it can be applied using standard pump sprays.
Gel creams
These are characterized by a slightly transparent, gel-like appearance and a light and fresh feel when first applied to the skin. This texture can be created by combining a polymeric thickener or polymeric emulsifier with a traditional emulsifier or by using a polymeric emulsifier on its own. Emulsifying sodium polyacrylate is an ideal ingredient for emulsion textures as it swells up on contact with water, forming a hydrogel with a three-dimensional network (Figure 2). Oil droplets become trapped in the cavities of the hydrogel network, enabling an o/w gel to form. Its structure ensures the formulation has long-term stability and accounts for the polymer’s emulsifying properties. Gel creams using this polymer are easy to apply, spread well and feel particularly smooth and light on the skin. The latter can be further improved by combining the polymer with ethanol. Even to the point of emulsifier-free concepts, sodium polyacrylate allows for exceptionally light sensorial aesthetics (Formulation 1). The system ensures a high degree of flexibility in the formulation of the oil phase and as a result a wide variety of viscosities and sensory properties are possible. The creation of sprayable formulations using emulsifying sodium polyacrylate is also possible. A further modification of emulsifier-free gel creams can be achieved by the addition of only a small amount of a new sensory wax (pentaerithityl distearate), which increases the cushion and care of such formulations.
O/W creams and lotions
The amount of thickener used and the extent of the interior phase determines whether a product is a cream or a lotion. A variety of different o/w emulsifiers comprising building blocks with or without ethoxylates can be used to achieve this, with consistency waxes being used to stabilize the formulation and control viscosity (Formulation 2).
A polyethylene glycol-free, self-emulsifying cream base, such as cetearyl glucoside and cetearyl alcohol, can be used to promote the formation of lamellar structures similar to the lipid bilayer structures in the skin. This type of emulsifier base is ideal for creating light to rich emulsions with a creamy yet powdery texture.
A holistic approach
From how a product looks when first opened to how it feels when applied on the skin, the texture of a skin care product is vital to how it is marketed and positioned. Speciality chemical suppliers must provide manufacturers with excellent raw materials and innovative formulation expertise that enables their customers to develop cosmetic products in line with emerging market trends. Modifying the ingredients of a formulation can give products a wide range of food-like textures, resembling, for example, trendy grocery products like piña colada or crème brûlée. And by altering the appearance and incorporating the relevant fragrance, manufacturers can produce tailor-made skin care products that deliver top quality performance while also meeting consumer demand in terms of relaxation and well-being.
Authors & contact
Bettina Jackwerth, global marketing director, Cognis Skin Care
Catherine Weichold, application technology manager, Cognis Skin Care, Germany
Tel +49 211 7940 2422
E-mail catherine.weichold@cognis.com