Method of hair damage assessment

Described is a method for measuring hair damage by copper uptake using in the process a simple hair volume measuring device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a method of assessing damage to human hair, and 
more particularly, to a method of quantifying human hair damage caused by 
hair treatment compositions applied thereto and damage caused to human 
hair by the environment. 
2. Description of the Prior Art 
Hair care is one of the most important parts of beauty care, and a large 
variety of hair treatment products are used for providing such care in the 
form of pre-shampoo conditioners, shampoos, after-shampoo conditioners, 
rinses, setting lotions, sprays, dyes, bleaches, permanent wave agents and 
the like. These products in addition to providing the desired result in 
the hair, such as luster, curl, combability, softness, color and an 
overall appealing look, also do damage to the hair, especially when used 
indiscriminantly without professional guidance. Damage to hair may also 
result from other sources, such as combing, humidity, dryness, dirt, 
sunrays, such as u.v. and infrared radiation, and pollution in the 
atmosphere. However, damage to hair occurs mostly in the form of physical 
and chemical changes in hair as a result of bleaching, oxidative dying, 
hair relaxing via alkaline relaxers and reducing waving and curling 
preparations. 
Assessment of hair damage is desirable, so that corrective action may be 
taken. Such corrective action may be: the utilization of products which do 
not cause damage or their damaging affect is minimal; eliminating the use 
of deleterious products; using products in proper sequence to circumvent 
further damage; or using products designed to repair hair damage. 
Measurement of hair damage is known in the prior art. For example, W. W. 
Edman and M. E. Marti, Journal of the Society of Cosmetic Chemists, pp: 
133-145, September 1960, report a study on properties of peroxide-bleached 
hair and use as a measure of hair damage the so-called 20% index, which is 
the ratio of work required to stretch the fiber 20 percent after treatment 
with a peroxide bleach to the work required to stretch the fiber 20% 
before treatment. To measure the 20% index a constant Elongation Tester is 
used. The same study also shows measurement of hair damage by 
"extension-at-break" using a Scott Tester. 
Measurement of hair damage via copper absorption is also known. U.S. Pat. 
No. 4,263,277 discloses a method for measuring hair damage by soaking a 
known weight of hair sample in a 0.1N tetraamine copper sulfate, followed 
by washing with water. The filtrate is then titrated against 0.1N sodium 
thiosulfate to determine the amount of copper absorbed by the hair. The 
damage to hair is assumed to correlate with the amount of copper absorbed 
by the hair sample. 
While methods like these to assess hair damage are appropriate for 
investigational and research purposes, they are not suitable for use by 
hair-care professionals or for home use. 
It is an object of the present invention to provide a method which can be 
easily applied by hair-care professionals as well as individuals to assess 
hair damage. 
It is another object of the present invention to provide a simple device 
for measuring the volume of fibrous materials as well as measuring the 
volume of hair samples used in the method of assessing hair damage. 
It is still another object of the present invention to provide stable 
copper solutions suitable for use in the method of assessing hair damage. 
These and other objects are accomplished in accordance with the following 
description of the invention. 
SUMMARY OF THE INVENTION 
It has now been discovered that hair damage can be assessed by a simple, 
inexpensive method based on measuring the intensity of color of a copper 
complex solution subsequent to the reaction of the copper complex with a 
known amount of hair. The steps of hair damage assessment comprises: 
(a) obtaining the weight of a hair sample; 
(b) subjecting said sample to a copper solution to effect attachment of 
positively charged copper ions to negatively charged groups in the hair; 
and 
(c) comparing color intensity of residual copper solution with color 
intensity of the copper solution prior to hair being subjected thereto. 
The weight of a hair sample is obtained by measuring the volume of the hair 
sample using the hair volume measuring device of the present invention and 
converting the volume so obtained to weight by the use of a mathematical 
equation or a table calculated therefrom. 
The hair volume measuring device comprises: a male member having a 
projection thereon; and a female member having a sample slot to receive 
and hold a sample as well as to engage said projection. Male and female 
members of the device are forced against each other compressing the hair 
sample placed in the sample slot. The width and length of the sample slot 
are known, and consequently the same dimensions of the sample are also 
known, while the height of the sample is obtained via measuring the 
distance between the surfaces of the male and female members of the 
device. 
DETAILED DESCRIPTION OF THE INVENTION 
Damage to hair caused by bleaching, oxidative dyeing, alkaline hair 
relaxers, reducing waving and curling preparations and the like results in 
the creation of negatively charged groups in the hair fiber. These groups 
readily react with the copper reagent. Thus, measurement of the amount of 
copper reacted with a known amount of hair is used to estimate the extent 
of hair damage. 
Copper uptake by hair must be based on a known quantity of hair, such as 
weight. While in a research environment the weighing of a hair sample can 
be easily accomplished by the use of an analytical balance, in beauty 
salons or in the homes the weighing of such light materials as hair cannot 
be done simply and economically. One of the objects of the present 
invention is accomplished by the provision of a simple device by which 
quantitative measurements of a small hair sample can be easily made. The 
device is used to measure hair volume which is then converted to hair 
weight through the use of an equation or appropriate table. 
HAIR VOLUME MEASURING DEVICE

DETAILED DESCRIPTION OF THE DRAWINGS 
The hair volume measuring device 10 of the present invention, by and large, 
is of a cube-shaped configuration comprising male and female members. It 
is made of metal, metal alloys or hard material such as plastic, 
porcelain, wood and glass by molding, casting and machining to desired 
precision using conventional technique of fabrication. 
As can be seen in FIGS. 1 and 2, the hair volume measuring device 10 
comprises: male members 12 having projection 14 extending therefrom; and 
female members 16 having a sample slot 18 to receive and hold hair sample 
20 and to engage projection 14. The width of the generally rectangular 
shape projection 14 is slightly smaller than the width of the generally 
rectangular shape sample slot 18 for proper mating engagement of the same. 
In use, hair sample 20 having a length longer than the length of sample 
slot 18, is placed into sample slot 18. Male member 12 is placed on female 
member 16 so that projection 14 engages sample slot 18 in a mating 
relationship exerting force on hair sample 20 and compressing the sample 
to assume a generally rectangular configuration as can best be seen in 
FIG. 2. Portions of the hair sample on both sides of the device extend 
outward as shown in FIG. 3. To obtain the proper volume of the sample, 
defined by the space the sample occupies in sample slot 18, the portions 
of the hair sample projecting outward on both sides of the device are cut 
with a sharp instrument 22, such as a razor blade, as shown in FIG. 4. 
Subsequent to cutting, the hair sample 20 assumes the configuration 24 
shown in FIG. 5. The length and width of this configuration is known from 
the predetermined dimensions of the sample slot, while the height of the 
same is measured by measuring the gap 26, shown in FIG. 2, between the 
surfaces of male member 12 and female member 16 of the device. 
FIGS. 6 and 7 show another embodiment of the hair volume measuring device 
of the present invention wherein like numbers denote like members and 
parts of the device shown in FIGS. 1-5. FIG. 6 is a perspective view of 
the embodiment in which, additionally, a measuring slot 28 is provided for 
measuring the height of a hair sample placed in sample slot 18 as 
previously described. Measuring device 30, such as a taper gauge, is 
inserted into measuring slot 28, as shown in FIG. 7, and the number on the 
measuring device that corresponds with the height of the sample is read. 
FIG. 8 is a perspective view of a further embodiment of the present 
invention wherein like numbers denote like members and parts of the 
embodiments shown in FIGS. 1-7. The device of FIG. 8 is substantially the 
same as the device of FIGS. 1-5, however, it additionally contains a pair 
of rods 32 in female member 16 and corresponding receiving members or 
holes 34 in male member 12 for engagement thereof. Upon use for volume 
measurement, rods 32 are inserted into corresponding receiving members on 
holes 34 and male member 12 is pressed against female member 16. The 
engagement of said rods with said holes help to maintain parallel 
alignment of the respective surfaces of the male and female members of the 
device. 
FIG. 9 is a perspective view of still another embodiment of the hair volume 
measuring device of the present invention wherein like numbers denote like 
members and parts of the embodiments shown in FIGS. 1-8. The device of 
FIG. 9 is substantially the same as the device of FIG. 8, however, it 
additionally contains measuring slot 28 the function of which was 
previously explained in the description of FIGS. 6 and 7. 
Measurement of hair volume is accomplished by placing a small sample of 
hair, having a length of at least as long as the length of the device, in 
the sample slot of the female member of the device and compressing the 
sample with the projection of the male member of the device. If sufficient 
hair has been placed in the sample slot, there will be a gap between the 
superimposed surfaces of the male and female members of the device. The 
distance between the surfaces, which is a measure of the thickness or 
height of the hair sample in the sample slot, is measured by a gauge such 
as an automotive feeler or taper gauge capable of measuring thickness in 
thousands of an inch. The gauge is inserted in the gap between the 
surfaces or in the measuring slot of the device especially provided for 
measuring purposes. Once the gauge reading has been recorded, the hair 
protruding from both sides of the sample slot is readily cut with a razor 
blade. The gauge reading is then used to determine the actual hair weight 
via the relationship of the least square line of best fit. 
The examples that follow will further illustrate the utilization of the 
hair volume measuring device of the present invention. 
EXAMPLE 1 
The volumes of virgin hair samples, obtained from well mixed commercial 
sources, were measured with the device of the present invention having the 
following dimensions: 
______________________________________ 
slot depth: 0.125" 
slot width: 0.045" 
slot length: 1.000" 
compression element height: 
0.055" 
compression element width: 
0.038" 
______________________________________ 
A feeler gauge was used to measure gap distance between male and female 
members of the block. Then the actual weights of the samples were taken on 
an analytical balance. 
Results are shown in Table I. 
TABLE I 
______________________________________ 
Virgin Hair 
Hair Weight, Mg 
Gauge No. Actual Calculated* 
______________________________________ 
4 44.3 40.1 
4 37.9 40.1 
4 37.7 40.1 
4 40.5 40.1 
4 40.7 40.1 
5 39.3 41.8 
5 44.1 41.8 
7 45.5 45.1 
7 42.0 45.1 
7 46.8 45.1 
8 46.0 46.6 
8 49.0 46.6 
8 45.5 46.6 
9 45.6 47.9 
9 47.3 47.9 
10 44.8 49.2 
11 53.5 50.4 
11 49.7 50.4 
12 50.9 51.5 
17 53.5 55.5 
18 55.3 56.0 
23 55.7 57.1 
24 58.8 57.0 
25 57.3 56.8 
______________________________________ 
*From the line of best fit 
Weight = 32.0 + 2.21 (gauge) - .0487 (Gauge).sup.2 
% Error: 3.8 .+-. 2.6% 
EXAMPLE 2 
The volumes of double bleached hair samples, obtained from well-mixed 
commercial sources, were measured with the hair volume measuring device of 
the present invention having the following dimensions: 
______________________________________ 
slot depth: 0.125" 
slot width: 0.045" 
slot length: 1.000" 
compression element height: 
0.055" 
compression element width: 
0.038". 
______________________________________ 
A feeler gauge was used to measure gap distance between male and female 
members of the block. Subsequently, the actual weights of the samples were 
taken on an analytical balance. Results are shown in Table II. 
TABLE II 
______________________________________ 
Double Bleached Hair 
Hair Weight, Mg. 
Gauge No. Actual Calculated* 
______________________________________ 
5 44.1 41.8 
6 46.6 43.5 
7 44.6 45.1 
9 49.9 47.9 
10 49.7 49.2 
11 51.2 49.2 
12 52.5 51.5 
15 54.9 54.2 
23 58.8 57.1 
______________________________________ 
*From the line of best fit 
Weight = 32.0 + 2.21 (Gauge) - .0487 (Gauge).sup.2 
% Error: 3.2 .+-. 2.0% 
EXAMPLE 3 
The volumes of hair samples, taken from 20 different subjects were measured 
with the device of the present invention having the following dimensions: 
______________________________________ 
slot depth: 0.150" 
slot width: 0.055" 
slot length: 0.500" 
compression element height: 
0.058" 
compression element width: 
0.043" 
______________________________________ 
A feeler gauge was used to measure gap distance between male and female 
members of the block. Subsequently, the actual weight of samples were 
taken on an analytical balance. Results, including percent error as weight 
difference between calculated and measured weights, are shown in Table 
III. 
TABLE III 
______________________________________ 
Caucasian Hair 
Hair Weight.sup.(1) 
Feeler Gauge No. 
Found Calculated 
Error % 
______________________________________ 
5 35.0 36.4 3.8 
5 36.1 " 0.8 
5 34.6 " 4.9 
5 38.0 " 4.4 
6 39.0 37.1 5.1 
6 36.4 " 1.9 
10 40.1 40.0 0.3 
10 40.6 " 1.5 
12 40.0 41.4 3.4 
14 45.6 42.9 6.3 
14 42.3 " 1.4 
14 42.6 " 0.7 
15 43.8 43.6 0.5 
15 42.1 " 3.4 
15 43.4 " 0.5 
16 45.3 44.3 2.3 
16 41.7 " 5.9 
16 44.5 " 0.5 
16 43.4 " 2.0 
17 48.3 45.0 7.3 
18 47.6 45.8 3.9 
28 51.5 52.9 2.6 
X = 2.6 
______________________________________ 
.sup.(1) From the relationship: Weight = .719 Gauge + 32.8 
EXAMPLE 4 
The volumes of hair samples were measured with the device of the present 
invention having the following dimensions: 
______________________________________ 
slot depth: 0.100" 
slot width: 0.045" 
slot length: 1.000" 
compression element height: 
0.055" 
compression element width: 
0.038". 
______________________________________ 
A taper gauge was used to measure gap distance between male and female 
members of the block. The actual weight of samples were taken on an 
analytical balance. Results, including percent error as weight difference 
between calculated and measured weights, are shown in Table IV. 
TABLE IV 
______________________________________ 
Hair 
Hair Weight.sup.(1) 
Taper Gauge No. 
Found Calculated 
Error % 
______________________________________ 
103 48.1 48.4 0.6 
105 50.8 50.3 0.9 
106 51.5 51.3 0.4 
106 52.4 51.3 2.1 
111 57.5 56.2 2.3 
113 57.0 58.1 1.9 
114 57.7 59.1 2.4 
120 64.2 64.9 1.0 
122 68.9 66.8 3.0 
123 62.7 67.8 8.1 
125 70.8 69.7 1.5 
129 76.0 73.6 3.1 
130 74.6 74.6 0.0 
X = 0.9 
______________________________________ 
.sup.(1) From line of best fit: Weight = 0.970 Gauge - 51.5 
The above-shown data illustrate that the hair volume measuring device of 
the present invention is well suited for obtaining the weight of a small 
sample based on the measurement of the volume of the sample. It is to be 
noted that, in addition to measuring the gap between the male and female 
members of the block by the use of a feeler gauge or taper gauge, other 
methods or devices could be used as well, such as an optical micrometer. 
Also, in addition to utilizing the device in connection with hair sample 
measurements, the same may be utilized with other fibrous materials both 
natural and synthetic. 
Upon obtaining the volume of a hair sample, its weight is calculated and 
the sample is placed into a vial, such as an optically clear 1/8 oz. screw 
capped bottle containing a copper solution of known or previously measured 
color intensity. Generally a non-volatile copper solution having Cu.sup.++ 
ions stabilized with a complexing agent which complexes with the 
Cu.sup.++, having a pH of about 9.0 to 9.5 is used in the practice of the 
present invention. The following formula is illustrative of formulations 
contemplated by the present invention. 
______________________________________ 
Sodium Tetraborate - 10H.sub. 2 O (buffer agent) 
3.81 g 
Copper Sulfate - 5H.sub. 2 O 
3.90 g 
Ethanolamine (complexing agent) 
3.99 g 
Purified H.sub.2 O qs to 1000 ml 
Final pH 9.2 
______________________________________ 
A complexing agent, such as ethanolamine, renders the solution stable for 
extended time periods. Illustrative of stability is the following data 
obtained on aging of the above-shown copper sulfate formula containing 
ethanolamine therein as the complexing agent. 
______________________________________ 
Copper Sulfate/Ethanolamine 
% Stability 
Time Room Temp. 40.degree. C. 
50.degree. C. 
______________________________________ 
1 year 97.5% 96.7% 95.1% 
2 years 95.1% 93.4% 90.9% 
______________________________________ 
The capped vial, containing the copper solution and hair sample is shaken, 
then heated for about a minute in boiling water to obtain a reaction 
between the copper reagent and negatively charged groups in the hair. The 
solution is then decanted into a cuvette and the color intensity measured. 
Color intensity measurement may be made by several methods including the 
following: 
(a) Color Chart Method in which the color of the decanted solution is 
matched with color strips of varying intensities on a color chart. 
Corresponding to the color intensity of the strips are numbers denoting 
extent of hair damage. 
(b) Color Tubes Method in which the color strips of the color chart method 
are replaced by sealed color tubes containing various concentrations of 
copper ions and the hair damage is estimated similarly as in (a). 
(c) Glass Slides Method in which comparison of color intensity of the 
sample vial is made with colored glass slides. 
(d) Electronic Optical Measurement methods instrumentally measuring color 
intensity such as, filter photometers and spectrophotometers. 
Alternatively to measuring copper concentration by measuring color 
intensity, the same can be measured by impendance measurement, in which 
the concentration of copper in solution is measured via the inverse 
relationship of concentration to impendance. 
Hair damage measurements were made utilizing the copper uptake method 
hereinbefore described and comparing the result obtained thereby with that 
of the Instron Stress/Strain Apparatus method. Hair damage measurement by 
the Instron Stress/Strain Apparatus is based on the force required to 
produce an elongation of 15% in hair length which force decreases with 
increasing hair damage. 
EXAMPLE 5 
Virgin hair samples were exposed to alkaline solution for varying length of 
time then washed free of alkali. Instron Stress/Strain and copper uptake 
measurements were made on the samples. Results are shown in Table V. 
TABLE V 
______________________________________ 
Increase in 
Relative Force Required 
Copper Uptake, 
to Produce 15% Elongation 
mg/g hair 
______________________________________ 
100 0.0 
96.36 4.44 
89.86 5.92 
89.77 7.44 
75.56 13.99 
77.26 14.50 
______________________________________ 
EXAMPLE 6 
Virgin hair samples were treated with thioglycolate for varying time 
periods followed by treatment with bromate simulating a typical hair 
waving treatment. The hair samples were then washed free of residual 
materials. Instron Stress/Strain and copper uptake measurements were made 
on the samples. Results are shown in Table VI. 
TABLE VI 
______________________________________ 
Increase in 
Relative Force Required 
Copper Uptake, 
to Produce a 15% Elongation 
mg/g hair 
______________________________________ 
100.00 0.00 
94.44 0.48 
82.35 5.84 
82.19 6.57 
78.27 7.38 
69.93 7.78 
69.20 8.11 
______________________________________ 
EXAMPLE 7 
Virgin hair samples were treated weith the typical bleaching agents, 
hydrogen peroxide and potassium persulfate for varying lengths of time. 
Subsequent to treatment, the samples were washed free of residuals. 
Instron Stress/Strain and copper uptake measurements were made on the 
samples. Results are shown in Table VII. 
TABLE VII 
______________________________________ 
Increase in 
Relative Force Required 
Copper Uptake 
to Produce 15% Elongation 
mg/g hair 
______________________________________ 
100.00 0.00 
99.05 1.54 
91.12 6.03 
83.12 11.05 
______________________________________ 
As can be ascertained from Tables V-VII, there exists a good correlation 
between results obtained by physical stress/strain measurement and that 
obtained by the copper uptake method of the present invention. 
It will be understood that the preceding examples have been given for 
illustration purposes only and that this invention is not limited to the 
specific embodiments disclosed therein. It will also be readily apparent 
to those skilled in the art that many variations can be made of the hair 
volume measuring device as well as the method of measuring hair damage by 
the copper uptake method, within the limits set forth without departing 
from the spirit and scope of the invention.