CHAPTER 23
Blade Shaving

Kevin Cowley¹, Kristina Vanoosthuyze¹, Gillian McFeat², and Keith Ertel^2,3

¹ Gillette Innovation Centre, Reading, UK

² Procter & Gamble Co., Cincinnati, OH, USA

³ KDE Scientific Consulting, LLC, Sheboygan, WI, USA

Introduction

Like many personal care practices, the roots of shaving lie in the prehistoric past. Hair removal for our cave‐dwelling ancestors was probably more about function than esthetics; hair could provide an additional handle for an adversary to grab during battle, it collected dirt and food, and it provided a home to insects and parasites. Flint blades possibly dating as far back as 30,000 BC are some of the earliest examples of shaving implements. Archeological evidence shows that materials such as horn, clamshell, or shark teeth were used to remove hair by scraping. Pulling or singeing the hair, while somewhat more painful, were also methods used to affect hair removal.

Attitudes toward hair became more varied in ancient times. The Egyptian aristocracy shaved not only their faces but also their bodies. The ancient Greeks viewed a beard as a sign of virility but Alexander the Great, who is said to have been obsessed with shaving, made the practice popular among Greek males. Greek women also shaved; a body free from hair was viewed as the ideal of beauty in Greek society. Shaving was viewed as a sign of degeneracy in early Roman society, but an influx of clean‐shaven foreigners gradually changed this attitude. For affluent Romans, shaving was performed by a skilled servant or at a barbershop, which was popularized in ancient Rome as a place of grooming and socializing. Shaving implements at this time were generally made from metals such as copper, gold, or iron.

The barbershop took on an expanded role in the Middle Ages. In these shops, barbers provided grooming services and routinely performed other duties such as bloodletting and minor surgical and dental procedures. Shaving injuries were common and the striped pole that is today associated with barbershops has its origin in these times, its red and white stripes symbolizing blood and the bandages that were used to cover the wound, respectively.

The Industrial Revolution heralded a number of advancements in shaving technology. The straight razor was first introduced in Sheffield, England, and became popular worldwide as a tool for facial shaving. While an improvement over earlier shaving implements, the straight razor dulled easily, required regular sharpening or stropping and a high skill level, and shaving injuries were still a problem, which earned it the nickname of “cutthroat razor.” Many credit Jean Jacques Perret with inventing the safety razor in 1762. His device, which he apparently did not patent, consisted of a guard that enclosed all but a small portion of the blade. Variations on the design followed from other inventors, many using comb‐like structures to limit blade contact with the skin. The Kampfe Brothers filed a patent in 1880 for a razor, marketed as the Star Safety Razor that used a “hoe” design in which the handle was mounted perpendicular to the blade housing. The blade, essentially a shortened straight razor, was held in place by metal clips. While generally successful, the blade in the Star Safety Razor still required stropping before each use.

In 1904, King C. Gillette introduced the real breakthrough that brought shaving to the masses. Unlike its predecessors, the Gillette Safety Razor used an inexpensive disposable blade that was replaced by the user when it became dull. The new razor quickly gained popularity due to a variety of promotional efforts, including a blades and razors marketing model pioneered by Gillette.

Shaving was not only promoted to males. The practice of shaving among females was prompted by the May 1915 issue of Harper’s Bazaar Magazine that featured a picture of a female model wearing a sleeveless evening gown and sporting hairless axillae. The Wilkinson Sword Company built on the idea by running a series of advertisements targeting women in the 1920s to promote the idea that underarm hair was not only unhygienic, it was also unfeminine. Sales of razor blades doubled over the next few years.

Razor developments during the next several decades were primarily limited to improvements in single blade technology, including the switch from carbon steel to stainless steel blade material in the 1960s introduced by Wilkinson Sword. This prevented corrosion thus increasing blade life. The next major change occurred in 1971 with the introduction of the Trac II, the first multiblade razor. Innovation has continued along this track and today consumers can choose from a variety of razor models having multiple blades contained in a disposable cartridge, with specialized designs available to meet the shaving needs of both sexes. The relatively simple appearance of these devices belies their sophistication; they are the product of years of development and technically advanced manufacturing processes.

Of course, not all shaving is done with a blade. Electric razors remove hair without drawing a blade across the skin. There are two basic types of electric razors, both relying on a scissor action to cut hairs using either an oscillatory or circular motion. When the razor is pressed against skin the hairs are forced up into holes in the foil and held in place while the blade moves against the foil to cut the trapped hairs. Colonel Jacob Schick patented the first electric razor in 1928. Electric razors were for many decades confined to use on dry skin, but some modern battery‐powered razors are designed for use in wet environments, including the shower.

Hair biology basics

Much of the hair targeted for removal by shaving or other means is terminal hair (i.e. hair that is generally longer, thicker, and more darkly pigmented than vellus hair). In prepubescent males and females, this hair is found primarily on the head and eyebrow regions, but with the onset of puberty, terminal hair begins to appear on areas of the body with androgen‐sensitive skin, including the face, axillae, and pubic region. Further, vellus hairs on some parts of the body, such as the beard area, may convert to terminal hairs under hormonal influence.

The pilosebaceous unit

A pilosebaceous unit comprises the hair follicle, the hair shaft, the sebaceous gland, and the arrector pili muscle. The hair follicle is the unit responsible for hair production. Hair growth is cyclical and depending on the stage of hair growth, the follicle extends to a depth as shallow as the upper dermis to as deep as the subcutaneous tissue during the active growth phase.

The hair shaft is the product of matrix cells in the hair bulb, a structure located at the base of the follicle. The hair shaft is made up primarily of keratins and binding material with a small amount of water. A terminal hair shaft comprises three concentric layers. Outermost is the cuticle, a layer of cells that on the external hair are flattened and overlapping. The cuticle serves a protective function for external hair, regulates the water content of the hair fiber, and is responsible for much of the shine that is associated with healthy hair. The cortex lies inside the cuticle and is composed of longitudinal keratin strands and melanin. This layer represents the majority of the hair shaft and is responsible for many of its structural qualities, e.g. elasticity and curl. The medulla is the innermost layer found in some terminal hair‐shafts, made up of large loosely connected cells, which contain keratin. Large intra‐ and intercellular air spaces in the medulla to some extent determine the sheen and color tones of the hair.

Each hair follicle is associated with a sebaceous gland. This gland lies in the dermis and produces sebum, a lipophilic material composed of wax monoesters, triglycerides, free fatty acids, and squalene. Sebum empties into the follicle lumen and provides a natural conditioner for the forming and already extruded hair. The arrector pili muscle is a microscopic band of smooth muscle tissue that connects the follicle to the dermis. In certain body sites, when stimulated the arrector pili muscle contracts and causes the external hair to stand more erect, resulting in the appearance of goose bumps.

Hair growth cycle

Hair growth is not a continuous process but occurs over a cycle that is conveniently divided into three stages; at any given time hairs on a given body site are at various points in this cycle. The dermal papilla orchestrates the hair growth cycle. Anagen is the phase of hair follicle re‐growth and hair generation. During this stage, the hair follicle grows downward into the dermis and epidermal cells that surround the dermal papilla undergo rapid division. As new cells form they push the older cells upward. The number of hairs in anagen varies according to body site. At any given time, approximately 80% of scalp hairs are in anagen. This is lower for beard and mustache hairs (around 70%) and only 20–30% for the legs and axillae. The length of the anagen phase also varies; on the scalp anagen typically lasts from 3 to 6 years, in the beard area this is closer to 1 year and in the mustache area anagen lasts from 4 to 14 weeks. Anagen is typically 16 weeks for the legs and axillae. The time in anagen determines the length of the hair produced [1].

Anagen is followed by catagen, a transitional phase in the hair growth cycle that sets the stage for production of a new follicle. In catagen, the existing follicle goes through controlled involution, with apoptosis of the majority of follicular keratinocytes and some follicular melanocytes. The bulb and suprabulbar regions are lost and the follicle moves upward, being no deeper than the upper dermis at phase end. The dermal papilla becomes more compact and moves upward to rest beneath the hair follicle bulge. On the scalp, catagen lasts from 14 to 21 days.

Telogen is a phase of follicular quiescence that follows catagen. The final cells synthesized during the previous cycle are dumped at the end of the hair shaft to form a “club” that holds the now nonliving hair in place. These hairs are lost by physical action (e.g. combing) or are pushed out by the new hair that grows during the next anagen phase. The percentage of follicles in telogen also varies by body site (e.g. 5–15% of scalp follicles are normally in telogen, whereas 30% of follicles on the beard area are normally in telogen and 70–80% of leg and axillae hairs). Telogen typically lasts for 2–3 months, although this is slightly longer for leg hairs [1].

Properties of hair – impact on shaving

The beard area of an adult male contains between 6000 and 25,000 hair fibers and beard growth rate has been reported in the literature to be 0.27 mm per 24 hours, although this can vary between individuals [2]. There are two types of hair fiber found in the beard area. Fine, nonpigmented vellus hairs are distributed among the coarser terminal hairs. While the literature abounds in publications on the properties of scalp hair, studies of beard hair are relatively scarce. Tolgyesi et al. [3] published the findings of a comparative study of beard and scalp terminal hair with respect to morphological, physical, and chemical characteristics. Scalp fibers were reported to have half the number of cuticle layers compared to beard hairs from the same subject (10–13 in facial hair, 5–7 in scalp hair). Scalp fibers also had smaller cross‐sectional areas (approximately half the area) and were less variable in shape than beard hairs, which exhibited asymmetrical, oblong, and trilobal shapes. These differences can be seen in (Figure 23.1). Thozhur et al. [4] further showed considerable variations in beard hair follicle shape and diameter within and between individuals. A number of factors contribute to this variation including anatomical location, ethnicity, age, and environmental factors.

The structural properties of the hair impact shaving. The force required to cut a hair increases with increasing fiber cross‐sectional area [5]. Thus, it requires more force to cut a larger fiber. Indeed, it requires almost three times the force to cut a beard hair compared to a scalp or leg hair. An important property of hair is that the force required to cut it can be greatly reduced by hydrating the hair. Hydration causes the hair to become significantly softer and much easier to cut so that it offers less resistance than dry hair to the blade and minimizes any discomfort.

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