Applied Colorimetry

By Claudio Terribile

This book was born with a dual purpose. The first is to provide the hairstylist a suitable tool to deal with the problems they encounter in their daily work. I am sure many times it just happened to have an inventory shortage or even to find ourselves out of stocks in the warehouse, and we had to remedy with resourcefulness and tricks acquired from the experience accumulated over the years in our profession. The second purpose is to provide a real teaching tool for all those who come to this world of theory, practice, and lots of creativity. Getting familiar with the issues of colorimetry and apply them with satisfactory results, is not easy. Contents of the book: - 1.0 Biology - 2.0 Chemistry - 3.0 Tricho-chemistry - 4.0 Tricho-care - 5.0 Chemicals to avoid - 6.o Applied colorimetry - 7.0 Conceptual maps - 8.0 Glossary - 9.0 l ndex - 10.0 References - 57 Figures - 18 Conceptual maps - 7 Form ulas - 7 Charts - 7 Tests and verifications

• Language: English
• Publisher: Youcanprint
• Release date: Jul 24, 2015
• ISBN: 9788891199621

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CHAPTER 1.0

HAIR BIOLOGY

« Biology is for man the most significant of all the sciences, one that helped, perhaps more than any other, to the formation of modern thought»

(Jacques Monod)

1.1 - HAIR MORPHOLOGY

Analysis

IIn this section I will analyze human hair from a morphological standpoint, and define its peculiarities according to its structure. This type of analysis should be the first to be carried out when you are facing your customer in order to achieve a planned goal.

Type

In its morphology, hair is divided into three types:

cylindrical shape (structurally smooth)

egg-shaped (structurally semi-wavy)

flattened shape (structurally frizzy)

Features

To make a careful judgment also keep in mind:

Texture:

■ (the circumference of the hair-shaft, hair is so marked as fine or coarse, depending on width)

Density:

■ (the number of hair on scalp)

Porosity:

■ (the hair’s ability to absorb moisture)

Elasticity:

■ (the ability of each strand of hair to stretch and then return to its initial length, wet hair can stretch up to 50%, dry hair not more than 30% of their initial length).

1.2 - PARAMETERS IN COLORIMETRY

When performing cosmetic coloring of hair, you must keep in mind some basic parameters, and understand how the color is going to interact with your hair:

■ the exact rate of coloring matters in your cosmetics

■ the dilution ratio of the cosmetics

■ the exposure time

■ the lightening power of the cosmetics

■ the coverage power of color

■ whether the brand of cosmetic color you use, best works either with high or low percentage of oxygen in your H2O2

if H2O2 is with higher volumes ↔ very bright cosmetic color

if H2O2 is with lower volumes ↔ poorly bright cosmetic color

■ the cosmetic color toning

■ it is also essential you know very well the lightening power of your ammonia (NH3) and your bleaching powder

■ the identification of the class where a specific hair belongs, because the latter will indicate various features of hair, helping you both in the coloring and the lightening process

■ the gradation of your natural color

■ the percentage of gray hair

■ to verify the presence of different color shades, reflections, steaks, etc. both on the whole length of hair and close to the head

■ whether there are any pre-existing abnormality of hair

1.3 - HAIR STRUCTURE

Speed

In the form of fluff, multiple strands of hair are already formed during the fifth month of the human fetal life. A strand of hair have a growth speed of about 0,01 in. per day (0,39 in. per month, about 3,5•10-9m/s, endured mostly between 10 and 11 am, and between 4 pm and 6 pm)¹, this value can greatly change, depending on the individual. Hair has a growth cycle of 2-6 years duration (although there are documented lifecycles performed over ten years span).

Hair lifecycle

At the end of each cycle, the strand of hair falls out and it is replaced. The hair cycle consists of a three-phase sequence:

1) anagen

2) catagen

3) telogen

Follicle inclination

The hair follicles are sloping about 75 ° on the scalp.

The shape differs in three types:

Cymotrichies: wavy or curly with oval section.

Lissotrichies: straight with round cross-section.

Ulotrichies: wolly and fizzy with a flat cross-section.

Fig. 1.1 Cymotrichies

Fig. 1.2 Lissotrichies

Fig. 1.3 Ulotrichies

The thickness of human hair varies greatly according to ethnic heritage, and it ranges from (fig. 1.4) a minimum of 0.06 mm to a maximum of 0.1 mm. The amount of follicles found at birth on the scalp is genetically specific. The estimate number of hairs is related to its natural color: in blonde heads it is 150,000 on average, 110,000 in brunettes, black and red hair are 100,000 - 90,000. The density of hair also varies depending on the areas of the scalp, and there is an average of 940 hairs per in².

Fig. 1.4 Hair under a microscope

Red hair

The red color in hair is due to a recessive gene, it has the probability of 1/4 to occur in a couple of parents which, although they do not have red hair, both have the presence of the above mentioned gene. For a couple of parents where both have red hair instead, there is the certainty that their children will have red hair.

Red hair is also associated with other bodily features, such as light skin and freckles.

Graying

Hair over the years tends to become white. This phenomenon, known as graying, has a natural cause due to the sudden and complete loss of the enzyme-exchange between tyrosine and melanocytes of the unit pilaris; it occurs generally between the age of 30-40, both for men and women. The main causes that influence the growth of gray hair in an individual, may be the most varied and they can range from genetic, metabolic, nutritional to psychological nature.

Albinism

Graying can occurs at an early age (thus not due to aging) due to a psychological trauma, or due to albinism.

1.4 - CUTICLE

In each strand of hair it is possible to locate three different parts:

Hair section

1) Hair shaft → outer to the skin

2) Root → connected to the erector muscle of hair

3) Bulb → where the generator matrix of hair is located

Germ cells

The matrix is the only part of hair that contains germ cells, these cells duplicate themselves and push up those born before, meanwhile keratin is processed making the strand of hair stiff.

Composition

The strand of hair is composed of three concentric parts as shown in (Fig. 1.5), and from the outermost to the innermost those parts are:

1) cuticle

2) cortex

3) medulla

The cuticle is the outer part, consisting of transparent and thin cells (0.2-0.5 micron² thick), this cells are arranged in a single vertical row at the root base, obliquely organized in scales assembling the hair shaft; the lower end of each scale is attached to the cortex while the upper end is detached (like an ear of wheat).

Fig. 1.5 Inner cross-section of the cuticle

1.5 - HAIR CORTEX

Given the location, the cuticle (Fig. 1.6) is the first to be damaged when hair has been abused (inadequate shampoos, perms, brushing, etc.).

The cortex³ is the middle part of the strand of hair and it is most significant component. The cells of cortex retain melanin, from which depends the color of hair.

Length

Cortex is the largest part, set up by larger cells, fuse shaped, 90 microns long and 5 microns wide (1 micron = 1 thousandth of a millimeter), these cells are vertically arranged in parallel rows; cortex contains a colored pigment, melanin, which tends to decrease with the age of individuals making their hair become white (the process of graying).

Chemical reactions occur in the cortex

From the above, it is clear that to decolorize hair, e.g. with hydrogen peroxide, it is necessary that the chemical reactions occur in the cortex, because the cuticle (the outer part) is not colored.

The microscopic examination at high magnification of the bleached strand of hair, shows the cuticle severely damaged or even completely vanished.

Fig. 1.6 Inner cross-section of the hair shaft

1.6 - MEDULLA

Inner part of the hair

The medulla⁴ (Fig. 1.7) represents the inner part of the strand of hair and it is formed by rounded cells, divided by air bearings.

Sometimes missing in the human species

The rounded cells are arranged in columns, generally separated from each other by air space (the entrained air has the crucial role of protecting from cold, for this reason the medulla in animals exceeds 50% of the total thickness of the strand of