436 JOURNAL OF COSMETIC SCIENCE
the technical water content is raised. This likely relates to the heightened swelling and an
accompanying degree of cuticle uplift. On top of this, tensile testing experiments show
the break stress decreasing with increased water content (for reasons described previously).
As highlighted earlier, breakage in fatigue experiments shows much more sizable effects
and produces alarming results.21 In short, there is overwhelming evidence for considerable
negatives associated with increasing water content in hair.
In this same consumer study, panelists were also asked to assess the same attributes in
conditioned and nonconditioned hair wherein the conditioned hair was sizably ranked
as “most moisturized.” These products have an undisputed positive effect on consumer
perception of this property, but this is not because the technical water content is being
altered. The primary technical function of these products is to coat the hair with an
aesthetically pleasing, lubricating layer. It is, therefore, concluded that a perception of
“dryness,” and conversely “moisturization,” is a tactile property of the hair rather than
that of the strict technical definition. To this end, “moisturization” and “hydration” claims
are commonplace on hair-care products without consternation as it is understood that the
propositions relate to the consumer’s view.
These technical evaluations of water content as a function of relative humidity are
performed by a gravimetric gas adsorption approach using commercial equipment that is
today termed Dynamic Vapor Sorption (Surface Measurement Systems, PA).29
HAIR SHINE
Shine is also an attribute that consumers frequently associate with healthy hair, whereby
dulling is a negative accompanying diminished well-being. Technically, this attribute would
Figure 14. The hair-water adsorption isotherm.

437 SUSTAINABLE HAIR
be presumed to relate to the ability for light to reflect off the hair surface, which frequently
prompts attempted measurement via simple commercial glossmeters. In actuality, the
situation is considerably more complicated and has been a topic of consternation within
our industry.33
Historically, goniophotometers were used to assess light reflecting off the surface of
individual fibers.34 However, as per discussion of hair strength, this is not how consumers
make appraisal. Hair shine is a whole head assessment and necessitates measurements on
hair arrays. Commercial equipment is available (Samba®, Bossa Nova Vision, CA, USA)
that operates based on the so-called polarized light approach described in the scientific
literature.35,36 As with the goniophotometer approach, measurement involves assessing the
ratio of cleanly reflecting light (specular reflection) to that which is scattered to some extent
(diffuse reflection). This reflection data can then be used in conjunction with any of a
number of equations in the scientific literature which calculate a “shine number” based on
some mathematical manipulation of the above ratio.
From a technical standpoint, it is often presumed that hair shine is diminished by
progressive cuticle degradation, which leads to less specular reflection. Yet, there are other
contributors.33 Hair color has a large role much higher technical values are associated with
increasing pigmentation. In hair array measurements, fiber alignment also has a significant
effect (light can reflect more cleanly off better aligned hair). The contribution from both of
these factors can easily outweigh that of the cuticle integrity. Moreover, contrary conclusions
can arise from the use of the different shine equations in the literature.
Consumer perception of their own hair dulling presumably arises from a combination of
the previously mentioned factors. There will likely be some cuticle degradation, maybe
some UV-induced lightening of the color, and perhaps somewhat more of a disheveled state
as manageability starts to become an issue. The scientific literature also teaches that clean,
healthy hair possesses the highest shine, and sebaceous or product buildup can also produce
dulling. Shampoos clean the hair surface and accordingly are often advertised to help
increase shine. However, the origins of this proposition relate to returning hair to a baseline
state, rather than any increase above that level. By the above treatise, waxy conditioner
deposits might be expected to dull hair, but they are overwhelmingly perceived as being
beneficial in this area. It is hypothesized that the improved manageability of conditioned
hair helps facilitate a neater appearance with better fiber alignment that accordingly gives
an improved shine perception. So-called shine serums often utilize oils that coat the hair
surface and fill in surface asperities to facilitate reflection.
OTHER VISUAL PROPERTIES
Often certain consumer words and expressions are so commonplace in our industry that it
might seem they have well-established scientific equivalents. Yet, it is worth remembering
that consumer attributes are often very nebulous terms that likely mean different things to
different people. One such example might be frizz. To some, this expression might relate
to an unruliness that hinders manageability and/or style creation (either innately or as a
result of an external stressor) to others, it might be the frustration associated with the
progressive loss of a desired style that took considerable time and effort to create. While
it is difficult to define what frizz is, it is likely easier to note what frizz is not: where very
straight, sleek, and highly aligned styles are clearly devoid of frizz. This prompted this