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In the curl community, lots of energy is invested into contemplating and analyzing the performance of hair care products. However, most consumers probably give little conscious thought to the appearance of their favorite products, although they are definitely influenced by this seemingly irrelevant property.

Not surprisingly, product formulators spend a lot of time optimizing products to make them visually appealing to a consumer. The incorporation of pearlizing agents, opacifiers, and artificial colors are all methods used to create products that give the visual impression of luxury.

Why do products need cosmetic enhancement?

Shampoos and conditioners are mixtures known as oil-in-water emulsions. The major component is water, with various types of surfactants, emulsifiers, and oil-phase components dispersed into the aqueous phase via formation of micelles. Oftentimes, the concentration of non-water soluble ingredients is sufficiently high to render the micelles larger than the wavelength of visible light. This causes light to be scattered, creating a cloudy solution. Hazy solutions are not regarded as appealing by most consumers, as they can give the perception of not being clean or pure.

Another potentially unpleasant phenomenon is that certain useful ingredients can impart a yellow or amber hue to the finished product. This subtle discoloration can make consumers uneasy, as that color is often associated with spoilage or rancidity. A bright white or creamy ivory colored product is generally rated as cleaner and more attractive.

It is the goal of formulating chemists to create a product that appeals to all of the senses of their consumers, so they take definite measures to make their products more visually attractive. Happily, the solutions developed are not only capable of masking cloudiness or yellowing, but can also yield a highly pleasing final product.

How do they do it?

There are several different approaches a formulator can take to improve the appearance of her product. One technique popular in the 1970's was to cover any yellow or amber hues by using enough blue and/or green dye to create a blue or green product. These were not very natural-looking and were often fairly runny in consistency.

Current approaches seem to favor the use of only enough color to counteract the yellow and create a white or ivory product. Another trend for brands that market products as "natural" is to use a mixture of red, blue, and yellow dyes to create a brownish products that remind the consumer of clay or earth.

An additional method to overcome hazy solutions is to incorporate opacifiers into the formula. These materials create a homogeneous, solidly opaque appearance to the shampoo or conditioner. Dow markets a line of polymers intended for this use, and the marketing materials say they create a “rich, creamy look, with a dense uniform opacity.” The use of polymers also helps to increase the viscosity of the system, which consumers also interpret as thick and luxurious.

Dow has several different polymers available for this purpose, each specially synthesized to be compatible with different common systems. Ethalkonium chloride acrylate/HEMA/styrene copolymer is cationically charged and is compatible with most cationic conditioning products. They also have an anionic opacifier for use in shampoos, soaps, liquid hand soap, and body washes, all of which traditionally rely upon anionic surfactants for cleansing purposes.

A non-ionic version is sufficiently flexible to be incorporated into a variety of types of formulations, and is especially useful in silicone-containing formulae. These types of materials make bright white shampoos and conditioners that are creamy and thick.

Pretty in Pearls

Perhaps a favorite method for overcoming problems with cloudiness and yellow hue in personal care products is to use pearlizing agents. These materials not only act as opacifiers, but also impart an iridescent luster to a product that is considered to be highly attractive to consumers.

This look can be achieved by using naturally-occurring minerals such as marine aragonite powder (real pearl) or titanium oxide-coated mica particles, but more often is achieved via use of synthetic fatty acid ether esters. The synthetic esters most often used are ethylene glycol distearate (EGDS) and ethylene glycol monostearate (EGMS). Others are PEG-8 dioleate, myristyl myristate, ethylene glycol dipalmitate, and other esters. These materials crystallize in solution into flat platelets that have a very high refractive index. Optical interference from these platelets creates a pearlescent appearance in products containing these materials.

One drawback to using materials such as EGDS is that the somewhat tricky process for adding them during manufacturing.  Temperatures must be elevated above the melting point of the EGDS. In order to obtain the highest quality pearlescence, the crystallization process must be carefully controlled, which means that the mixing rate and forces must be carefully monitored, and the rate of cooling must also be very controlled.  Crystals of just the right size,  and of the smoothest, most regular shape provide the best, most lustrous appearance.  This can be costly and troublesome.

Chemical suppliers are vying for market share for these types of relatively simple-to-make ingredients. One way they seek to differentiate themselves is to provide blends that contain these pearlizing agents already dispersed into surfactant-containing mixtures. These blends have varying features to recommend them, depending upon the package, but typically, the most valuable feature is that they can be processed at cold temperatures and require much less oversight of the manufacturing process to develop the optimal crystalline structures. They are also often times more stable in typical storage conditions. Ease of processing reduces costs for the manufacturer, which translates into these pearlized products being more affordable for the consumer.

These materials can have some slight humectant or moisturizing properties for hair or skin. Generally though, they are not going to significantly impact the performance properties of your favorite shampoo or conditioner. Most opacifiers and pearlizers have sufficient polar or amphiphilic character as to be easily removed from hair (if they remain on the hair in the first place) via a conditioner wash or mild shampoo cleanse.

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Final Thoughts

So the next time you pick up a product, in addition to considering its performance and fragrance, take a moment to ponder and appreciate its appearance as well. A bunch of scientists somewhere put a lot of time and thought into making it attractive to you. It is an important part of the whole package.

 

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