soda-hydrogen peroxide toothpaste, hair bleach, and epoxy adhesive (not related to personal care but worthy of note) require separation of components prior to use for valid chemical reasons yet are not multifunctional.

2.4 Packaging and Dispensing Options

A number of packaging systems have been designed to sequester the component formulas of multifunctional products, yet allow them to be conveniently codis-pensed. They have taken a number of forms including the following: two collapsible tubes, or rigid containers, that are maintained side by side; and a single, rigid-walled container with two separate chambers (e.g., double-barreled syringe of the type commonly employed for epoxy adhesives). An overriding concern in the design of such containers is to ensure that the final unit does not become too cumbersome in size or shape to allow for ergonomically convenient dispensing.

Dispensing methods vary from the co-pouring/co-pumping of liquids from rigid-walled containers (either two containers that are maintained in tandem or a single container with two chambers), to the co-squeezing of viscous materials from collapsible tubes, to the co-extrusion of very viscous materials by plunger from a dual-chambered rigid container (e.g., system employed to dispense Chese-brough-Pond's Mentadent baking soda-hydrogen peroxide toothpaste [3]; the double-barreled syringe employed with epoxy adhesives). The dispensed material may vary in form, from two separate streams or ribbons dispensed in close proximity to one flow of product containing two separate streams or ribbons to one flow of product in which the streams or ribbons are co-mixed. The two latter examples require the use of a component designed to induce the material dispensed from two orifices to converge into one flow, typically a Y-shaped fitment. The final example, in which the streams or ribbons are co-mixed during dispensing, also requires the incorporation into this codispensing component of a swirl chamber or a series of baffles [4].

It is important to recognize in the design of such systems that the consumer places great conscious, or subconscious, importance on their ability to dispense the entire contents of the unit. Further, dissatisfaction in this regard cannot be assuaged by simply overfilling the product to deliver the label-stated quantity, since the consumer rarely determines the amount of product that has been dispensed. (Some marketers have taken the additional step of advising the consumer, via label copy, that the package is designed to deliver the contents stated on the label even though some product may remain in the container.) For a more comprehensive discussion of this general subject the reader is encouraged to refer to | the chapter, The Role of Packaging in Multifunctional Products.

2.5 Codispensing Aerosols

Through the years, a variety of devices have been developed to codispense aerosolized products consisting of two liquid components that must be kept apart t prior to dispensing. While the predominant commercial application of these devices has been to dispense single-function products with special features (such as self-heating shave creams, notably Gillette's Hot One), they are described in this chapter because their design principles are highly applicable to multifunctional products. It also should be noted that they were commercially employed (by Clairol) for oxidation hair dyes, which the writer considers to be multi functional (because hair is bleached during the dying process).

Garnering a great amount of industry interest during the mid-1960s and early 1970s, the earliest of such devices depended on unique valving that codis-pensed product from two separated sources within the same aerosol can. One source was the can itself, from which liquid was dispensed via a conventional dip-tube, like a conventional aerosol. The other source was a pouch (or mini-container) affixed to the valve housing, rendering its liquid contents directly available for dispensing. Liquid from each source was then codispensed at a predetermined ratio, upon actuation of the aerosol valve. One of the significant failings of these systems was their inability to maintain this predetermined dispensing ratio throughout the functional life of the unit. This had the potential to lead to product failure and to cause consumer irritation. For some formulations, it was also very difficult to prevent cross-contamination of the two liquids within the unit. Because of these issues and for a variety of other reasons, the two-source dispensing systems are no longer commercially available.

More modern attempts at codispensing aerosols have been based on the simultaneous dispensing of two separate aerosol units through a device that combines the dispensed product into a single stream. Japanese companies have commercialized several hair dye products that are dispensed (and applied) through a comb fitted to the outermost portion of the unit. A significantly improved dispensing system, whereby the contents of the two aerosol units are co-mixed via a system of baffles, has been introduced in the United States [5].

2.6 Strategic Use of Aesthetic Properties

As briefly alluded to earlier in relation to product form, a number of halo signals may be employed to encourage the purchase of multifunctional products and to reinforce consumer satisfaction with their performance. The visual presence of a second entity is likely to have the most potent impact in this regard. This second entity may be a separate phase (layer, particles, beads) within a single component product, or it may take the form of a second component. Regardless, it provides the user with seemingly concrete evidence of multifunctionality.

Further halo support may be gained through the use of fragrance, color, and «

viscosity as with conventional products. Among the various categories of multifunctional products, the strategic design of aesthetic properties is most difficult for | homogeneous single-phase formulas (Table 4, category 1.a), since at least two |

Table 5 Aesthetic Parameters Supporting Cleanliness for a Two-in-One Shampoo


1. Fragrance: citrus or evergreen bouquet

2. Color: maize, light blue, light green

3. Viscosity: lower end of acceptable range functionalities must be considered, yet only one set of parameters may be established. Here it is necessary to decide which set of functional properties it is most judicious to support. In the case of two-in-one shampoos, where the user is frequently concerned about an undesirable conditioning residue on one hair, it may be strategically advisable to support cleanliness, as opposed to conditioning performance (Table 5). In testimony to the complexity of shaping aesthetic properties for such products, it must be noted that the parameters supporting the product's tendency to leave hair clean are, for the most part, in direct opposition to those supporting its ability to condition.

Multifunctional products that contain, or comprise, more than one entity (layer, beads, or separate components) provide the opportunity to design/employ each aesthetic attribute to reinforce the marketing position of each entity. For example, codispensed tandem tubes containing skin cleanser and moisturizer allow for the application of conventional wisdom related to the aesthetic properties of each component—with the additional requirement that they do not conflict with one another when co-mixed. Thus a white cleanser with low level of multinote/nonspe-cific clean fragrance might be paired with a light almond, pink, or blue moisturizer with a low level of nurturing (vanilla, almond) bouquet fragrance.

Such products also allow the use of "relative aesthetics" to support functionality. Here, for example, while both components are creams, the deployment of a relatively reduced viscosity for the cleansing component (compared with that of the moisturizing component) would tend to support its ability to clean and leave the skin free of residue. Conversely, the relatively higher viscosity of the moisturizing component would enhance the perception that it was rich in moisturizers and other beneficial ingredients. Here too, regardless of hue, a relatively lighter intensity of color would support cleansing, as opposed to moisturizing.


3.1 Performance Testing !

The functional evaluation of formulations may be considered as a continuum, starting with instrumental laboratory evaluations and ending with consumer/market testing. The laboratory phase of this progression enjoys the greater control of envi ronmental conditions, substrate uniformity, application parameters, test methods, and so on, and therefore provides the greatest amount of sensitivity, accuracy, reproducibility, and objectivity. Conversely, consumer testing, with less control of these parameters, provides less sensitivity, accuracy, reproducibility, and objectivity, but for many of the same reasons provides results that are more representative of reallife product usage than those gained from instrumental laboratory investigation.

Of critical importance to the evaluation of multifunctional products, and in direct contradiction to most laboratory test methods; however, consumer testing cannot evaluate individual performance properties without including the impact of other performance (as well as aesthetic) properties. In some cases this limitation is exacerbated by inherent conflicts among formula functionalities (e.g., cleansing vs moisturizing in a moisturizing body wash; cleansing vs conditioning in a two-in-one shampoo). For these reasons it is even more essential for multifunctional products than for conventional products that testing be conducted at various points of this continuum.

It is highly recommended that the evaluation of multifunctional products begin in the laboratory, where each functional characteristic may be evaluated separately on an objective basis. It is there, and only there, that the formulator can learn how well prototypes deliver each functionality (preferably in comparison with standards established in a new product description document, see Sec. 1). Then, and only if warranted by the results of these studies, testing must be conducted to determine the combined impact of the formula's multifunctional properties in the test salon and amongst consumers. Again, such testing more closely approximates the usage patterns and challenges that products encounter in real life. As is the case for conventional products, overt steps may be required to eliminate the impact of aesthetic properties on consumer-perceived performance during these studies.

As a practical note, considering the rigors necessary to conduct meaningful laboratory studies, it may be thought more convenient and expedient to bypass this phase and proceed directly to salon, clinical, or consumer evaluations. This temptation must be resisted, since without the foundation of sound laboratory-derived knowledge, this practice is likely to provide false positives or negatives based on the interference of other performance characteristics or aesthetic properties, with the result of an inferior product proceeding to market or a superior formula being discarded. It must always be remembered that if a performance-related characteristic is apparent in salon/clinical trials and/or consumer testing but is not detectable under highly controlled laboratory conditions, it probably does not exist. §

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