VINEET YAGNIK BIOLOGY EE

CANADIAN ACADEMY

The effects of cyclical bleaching on hair strength

Vineet Chetan Yagnik

IB Candidate Number: 000155-0038

2/12/2014

Word Count: 3,915

The research question of this extended essay is the following: “What are the effects of the number of

bleaching cycles on the hair strength of female Asian hair?” Our experiment consisted of bleaching 27

hair switches for 1-3 cycles. The bleaching time ranged from 0 to 120 minutes, in 15 minute increments

(Further information on this can be obtained in appendix A). We used a self-made method of measuring

hair strength. Our method consisted of finding average hair diameter and the hair’s tensile strength, then

dividing the tensile strength by the average hair diameter. We first bleached our switches then analyzed

the hairs from the switches to see their hair strength. We hypothesized that a greater amount of bleaching

cycles would result in lower hair strength. In conclusion, our data did not support our hypothesis.

However, with further qualitative analysis of the hair, we found out that, qualitatively, our hypothesis was

valid. Our data was inaccurate. This inaccuracy occurred possibly due to methodology errors and

unforeseen shrinking in the hairs. For further research, we recommended to use a previously test method

to evaluate hair strength—the 20 percent index—to reduce such errors and inaccuracies.

Word Count: 195

Vineet Chetan Yagnik IB Candidate Number: 000155-0038 February 12th, 2014 Word count: 3,915

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Table of Contents 0. Acknowledgements ................................................................................................................................... 3

1. Introduction ............................................................................................................................................... 4

Focus ......................................................................................................................................................... 4

The research question and its significance ........................................................................................... 4

The hair structure ................................................................................................................................. 4

The bleaching process ........................................................................................................................... 4

Hair strength measurement and brief introduction on experiment method .......................................... 5

Hypothesis ................................................................................................................................................ 5

HNULL ..................................................................................................................................................... 5

HALTERNATIVE............................................................................................................................................ 5

2. Variables ................................................................................................................................................... 5

Independent ........................................................................................................................................... 5

Dependent ............................................................................................................................................. 6

Controlled ............................................................................................................................................. 6

Uncontrollable ....................................................................................................................................... 7

3. Method ...................................................................................................................................................... 7

Materials ............................................................................................................................................... 7

Method .................................................................................................................................................. 8

4. Data ......................................................................................................................................................... 11

Raw data ............................................................................................................................................. 11

Processed data .................................................................................................................................... 11

5. Analysis .................................................................................................................................................. 13

Our data and our hypothesis ............................................................................................................... 13

Explanation of results ......................................................................................................................... 14

Qualitative evidence for hypothesis validity ....................................................................................... 14

Analysis of reliability and validity of our data.................................................................................... 15

T. Test .................................................................................................................................................. 15

Future improvements to ensure valid, reliable quantitative data ....................................................... 15

Storage of hair .................................................................................................................................... 16

More trials .......................................................................................................................................... 16


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6. Conclusion .............................................................................................................................................. 16

7. Works Cited ............................................................................................................................................. 16

Works Cited ................................................................................................................................................. 16

Appendix A: Switch number and time+cycle information ...................................................................... 18

Appendix B: Raw data ............................................................................................................................. 19


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0. Acknowledgements

Firstly, I would like to thank my dad for helping me so much throughout this extended essay. I

would also like to thank Mr. Dave Ferguson, my EE advisor and biology teacher, for his help and

feedback on the EE. I also thank Proctor and Gamble Japan for letting me borrow their resources and

their lab. This would not be possible without all of your help. Thank you very much!


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1. Introduction

Focus

The research question and its significance

The research question of this extended essay is: “What are the effects of the number of bleaching cycles

on the hair strength of female Asian hair?”

This research is important as millions of people around the world bleach their hair. Statistics show that

almost 75% of women in America color their hair [1]. Coloring usually involves bleaching. With

widespread use of bleaching, it is important for us to understand the process of bleaching. Cyclical

bleaching is also popular. While significant research has been conducted on the effects of bleaching on

the human hair on hair strength, no research has been conducted on cyclical bleaching. We know effects

of a single cycle of bleach, however what are the effects of the second or third cycle?

The hair structure

Hairs have 3 main layers. [2] Figure 1.1 shows us a diagram of the layers of the human hair.

Figure 1.1: Cross section of human hair. Diagram obtained from [2]

The outermost layer of hair is called the

cuticle. It consists of overlapping ‘scales’ of

protein and lipids [3]. The cortex is the next

layer—it is the thickest hair layer and gives

the hair its color. The innermost layer is the

medulla. The medulla is the hollow center of

the hair. The cell membrane complex (CMC)

is the ‘glue’ of the hair and keeps all the

layers of the hair together [2]. The destruction of the CMC can result in the disintegration of the cuticle

[4].

The bleaching process

Bleach works by oxidizing a plethora of different compounds in the hair [5]. This results in the lightening

of hair that we desire. However, Wolfram et. al [6] showed that bleach also oxidizes the bonds in various


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hair protein, rendering the proteins and affecting hair strength. Experiments have all shown such results—

more bleaching results in a decrease in hair strength [7] [8] [6].

Hair strength measurement and brief introduction on experiment method

We will generate data by bleaching various different hair switches for different times and different

bleaching cycles. We will then sample individual strands of hair and evaluate the hair strength.

We do not have the complicated materials required for more complicated methods, so we will use a self-

created method of hair strength measurement. Our method looks at tensile strength and the average hair

diameter. We divide the tensile strength by average hair diameter to get a relative value for hair strength,

with units g/µm. Our experiment will work by bleaching hairs for a range of times in 1-3 cycles and then

measuring the hair strength on said hairs.

Hypothesis

HNULL

There is no relation between the number of bleaching cycles and the hair strength of female Asian hair.

HALTERNATIVE

If we put hairs through a greater amount of bleaching cycles, the hair strength will decrease.

Explanation of alternative hypothesis

We know from past research that more bleaching time causes more hair damage [6-7]. Additional

bleaching cycles mean more bleaching time, resulting in a greater decrease in hair strength. In

addition, an extra bleaching cycle also means that bleach will need to repenetrate the hair with

every cycle.

To get inside the hair, bleach needs to pass through the cuticle. This requires the bleach to travel

through the CMC. Repeat entries through the CMC could possible result in complete damage of

the CMC, causing the cuticle to detach [4]. While the cuticle does not affect the structural

strength of hair [8], complete damage of the CMC does [4]. Not only that, as “self-repair is

impossible” [9] for hair, the CMC cannot regenerate.

Due to these various damage factors, I hypothesize more bleaching cycles will result in a greater

decrease in hair strength.

2. Variables

Independent Figure 2.1: Table showing independent variables

Variable Unit Range

Bleaching cycles N/A 1-3 cycles, 1 cycle increments


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Dependent Figure 2.2: Table showing dependent variables

Variable Units Method of measurement

Hair strength g/µm Dividing the tensile strength by the average hair

diameter.

Controlled

Figure 2.3: Table showing controlled variables

Variable Effect Method of Control

Dirt on/ inside hair Can possibly affect hair strength Wash hair before bleaching by

putting under running water for

15 minutes

Bleach remains on hair

after bleaching

Can cause hair to be oxidized for a greater amount of time than

needed.

Same as dirt on/inside hair

Humidity and

Temperature

As Speakman, et al [10] and Menkart, et al [11] observed, there

are differences in the tensile strength of hairs in different

humidity environments. Through research conducted by

Robbins [12] and Rebenfeld [13], evidence was provided that

tensile strength changed with temperature, too.

Data collection and hair drying

(for 24 hours) will be conducted

in a room that is controlled at

65% humidity and 25°C

Moisture on hand getting

on hair

The moisture acts the same way as humidity. Touching hairs

will cause the moisture levels of certain sections of the hair to

change and thus affect the cuticle in that portion.

This experiment will require the

use of nitrile gloves throughout.

Bare hands will not make

contact with the hair at any point

in the experiment or the

preparation of the hair.

Ethnicity of hair Hair from different ethnicities, locations and genders have

different physical and chemical qualities [11]. Different hairs

will show different reactions to the bleaching

We will control our hair to only

that of Asian females that

originate from the scalp.

Previously damaged hair Using damaged hair can result in a preexisting low hair

strength and can affect our results.

We will use undamaged, virgin

hair.


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Uncontrollable

Figure 2.4: Table showing uncontrollable variables

Variable Effect

Temperature and humidity when bleaching During the process of bleaching, humidity and temperature will

not be controlled for. This could temporarily affect hair strength.

Bleach The bleach I will use is not mass produced—we have to make it

using a formula. Thus, we will see slight variations in the bleach

whenever it is made due to uncertainty. Every bleaching cycle

needs a new bleach to be ‘made’.

Biological variation As the hair switches we will be using will contain different hair

from different people, biological variation will play a role in the

effect of bleaching. Some hairs may not react according to theory

and cause variation in data.

Uncertainties of equipment All of our equipment contains uncertainties which we cannot

control for. This means that our data is never certain.

3. Method

Materials

1. 27 hair switches

a. Female Asian hair

b. A hair switch is a sample of hairs

2. A marker

3. 1 stand

4. 1 stand clip

5. Bleach

6. 1-5 liter beaker in which we will bleach the hair

7. Materials for bleach preparation

a. I cannot state the method for bleach preparation as is it P&G’s own peroxide-based bleach

which is protected.

8. Water

9. Timer (±0.01 seconds)

10. Tub

11. Piece of metal

12. Small magnet

13. Clip

14. Paper clip

15. Baggy

16. 45 coins

a. 15 ¥1, ¥5 and ¥10 coins

b. Before starting, weigh each type of coin by putting all 15 on an electronic balance and finding

the average weight of the type of coin.


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17. 100g mass

18. Electronic micrometer

a. We used a Mitutoyo ID-C112BS (±0.01)

19. Electronic Balance

a. We used a Mettler PM200 balance (±0.01)

20. Rod/spatula

21. Aluminum foil

22. Safety goggles

23. Nitrile gloves

24. Humidity and temperature controlled room

a. 25°C, 65%

25. Fume hood

Description of all equipment used

We have 3 electronic devices being used. Information on them is provided on Figure 3.1.

Figure 3.1: A table containing a list and description of all electronic devices used in this

experiment

Device Use SI units and

uncertainty

How to use

Digital

micrometer

To

determine

the

diameter

of a hair

strand

µm, ±0.01 You need to put a strand of hair into an opening in the

micrometer, and then shut the opening. An indicator shows the

diameter.

Electronic

balance

To

determine

the mass

of objects

g, ±0.01 You need to put your sample on the pressure plate of the

balance. An indicator on the balance will show mass of that

object. Remember to recalibrate the balance before every use.

Timer To keep

track of

time

s, ±0.01 When you press the start button, the timer will start. An

indicator on it will show the amount of time passed since the

start button was pressed. You can press the stop button to stop

the time from going on. You can use this to find the amount of

between two intervals.

Method

There are two phases to this experiment: the preparation phase and the data collection phase.

Preparation phase

Make sure to wear nitrile gloves and safety goggles throughout the preparation phase.

1. Preparation of switches

a. Use a marker to label the switches from 1 through 27.

i. These numbers will help us know how much time and how many cycles of

bleaching the switch needs to go through


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ii. Refer to appendix A for the full table which shows what switch number

corresponds with what time+cycles.

iii. Don’t write on the hairs. Write on the tape/clip that holds the hairs.

2. Bleach

a. Make the bleach.

i. We used a peroxide-based liquid bleach. I cannot disclose the formula as it is

P&G’s secret formula.

ii. Make sure to prepare the bleach under a fume hood.

iii. Make and use the bleach in a 1-5 liter beaker.

b. Wash the switches

i. All switches should be washed for 15 minutes.

1. Use a timer to keep track of the time.

ii. Washing consists of having a tub and a source of running distilled water. Water

should be entering the tub. The switches should be in this tub. The current of the

flowing water in the tub is necessary for the cleansing of the switches. There

should be no additional substances added in the tub.

c. Bleach the switches

i. Take all the switches and completely submerge them in the bleach. Be careful of

using your hands. Use a rod or a spatula. Make sure the bleaching occurs under a

fume hood.

ii. When the bleaching time of a switch approaches (once every 15 minutes), use a

spatula or rod to take the switch out of the bleach. In the first cycle, there will be

3 switches to take out at every time interval. In the second cycle, there will be 2

switches to take out at every time interval and in the third cycle there will only be

1.

1. Use a timer to keep track of the time.

iii. When a switch/switches are taken out, immediately wash them again for 15

minutes in the exact same way described in b.

d. Drying

i. Take the switches and put them in a humidity and temperature controlled room

1. Humidity: 65%

2. Temperature: 25°C

ii. The switches should be suspended in the air with the use of a stand and a clip.


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iii. Make sure none of the switches are touching each other.

iv. The switches should be dried for at least 24 hours.

e. Once dried, do the 2nd

cycle in the same way. Once 2nd

cycle has dried, do the 3rd

cycle.

Make sure to only bleach switches that have to go through the 2nd

and 3rd

cycles.

f. This whole process will be staggered. For example, 90 minutes into the bleaching, you

will be done washing the 75 minute switches and drying them while also getting ready to

take out the 90 minute switches from the bleach.

3. Making the measuring apparatus

a. Figure 3.2 shows what the tensile strength measuring apparatus needs to look like:

Figure 3.2: Schematic of what the tensile strength measuring apparatus should look like

i. A stand should hold a clip which holds a piece of metal.

ii. A small magnet should be attached to this piece of metal.

1. Hair strands should be clipped between the magnet and the metal.

2. The magnet needs to be strong enough to hold the hair while force is

being applied to it. If it is not, the hair will slip off.

iii. There should be a paper taped to the back of the metal such that 5cm of the paper

should hang down from the metal.

iv. We also need to set up another small system.

1. Get a clip, a paper clip and a small baggy. Shape the paper clip such that

it connects the clip and the small baggy together.

a. Weigh the smaller apparatus and note its mass.


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Data collection phase

You don’t need safety goggles now however nitrile gloves are still important. You can never touch

the hairs with your bare hands.

4. Obtain hair switch with time+cycles that you want to sample

a. You will need 10 samples from every hair switch, including the three 0 minute (control)

switches.

5. Cut a strand of hair from the switch.

6. Clip the strand of hair between the metal and the magnet.

a. Make sure it’s still in its original orientation—stem up, tip down.

7. Using the paper as a reference, we need to attach the clip of the smaller apparatus on the hair such

that the portion between the magnet and the clip is 5cm long.

8. The average diameter needs to be measured first. Take 6 random samples using the electronic

micrometer of the section of hair and average it out.

9. Measuring tensile strength involves the baggy. Add coins into the baggy until the hair breaks.

Add the mass of the baggy to the total mass of the coins put into the baggy and that is the tensile

strength of the hair.

a. If all the coins have been put in the baggy and the hair is still intact, carefully take all the

coins out of the baggy, put in the 100g mass and then keep on adding coins.

To ensure reliability of data, we will have 27 samples with 10 trials each, giving us a total of 270 data

points. This should ensure a sufficient data set for us to evaluate our hypothesis and formulate a

conclusion.

4. Data

Raw data

Our raw data is located in Appendix B.

Processed data

The following is our processed data.


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Figure 4.1: Raw data on average hair strength in various times and cycles

Time (minutes)

0 15 30 45 60 75 90 105 120

Cycle 1 Average

Hair strength

(g/µm)

1.06 1.11 1.09 1.05 0.93 0.96 0.98 0.82 0.80

Cycle 2 Average

Hair strength

(g/µm)

1.14 1.11 1.15 1.21 1.06 1.00 0.91 0.82 0.83

Cycle 3 Average

Hair strength

(g/µm)

1.16 1.02 0.83 1.14 1.05 0.93 0.91 0.87 0.80

Figure 4.2: 95% confidence interval (CI) data for the average hair strengths in various times and cycles

Time (minutes)

0 15 30 45 60 75 90 105 120

1 cycle

95% CI

0.14 0.13 0.13 0.14 0.10 0.05 0.12 0.13 0.11

2 cycle

95% CI

0.16 0.14 0.12 0.15 0.15 0.12 0.11 0.11 0.12

3 cycle

95% CI

0.13 0.11 0.13 0.09 0.13 0.20 0.21 0.20 0.12


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5. Analysis

Our data and our hypothesis

Our data did not support our hypothesis. Our hypothesis was the following: If we bleach hair for a greater

amount of cycles, it will result in lower hair strength. In terms of our research question, it meant that there

are no effects of the number of bleaching cycles on the hair strength of female Asian scalp hair.

Our processed data is shown in Figure 4.1 and 4.2 and is visualized in Figure 4.3. Figure 4.3 shows us

declining hair strength with time in all three cycles. However, with closer inspection, we can see that the

data may not be valid: the 2nd

cycle data shows that our hair strength actually improved with a second

cycle. After 100 minutes, our data shows that the 3 cycle hairs are stronger than the 1 cycle hairs. Hair

cannot self-repair and our hair samples weren’t exposed to repairing agents or damaging agents. Our data

supports the idea that the bleaching cycles don’t affect hair strength.

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

0 20 40 60 80 100 120 140

Hai

r st

ren

gth

(g/

µm

)

Time (minutes) (±0.01)

Figure 4.3: Graph visualizing data from table 4.1 and 4.2

1 cycle

2 cycle

3 cycle

1 cycle

2 cycles

3 cycles


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Explanation of results

Our quantitative data shows that there is no relation between bleaching cycles and hair strength. Our

qualitative evidence, in the form of scanning electron microscope (SEM) pictures, however, suggests that

our hypothesis is valid and our data is invalid.

Qualitative evidence for hypothesis validity

Figure 5.1: SEM images of two hair samples that we bleached (120 minutes 1 cycle and 120 minutes 3 cycle)

along with annotations to point out hair destruction

We can see clear evidence of hair damage on the SEM images obtained of our samples of hair. We can

see evidence of cuticle removal, CMC damage and shrinkage. While cuticle removal has no effect on the

hair strength, it is evidence for complete CMC damage [8]. Complete CMC damage results in a decrease

in hair strength [2]. There is also further oxidative damage on the 3 cycle hair. Thus, qualitatively and

theoretically we know that there should be a decrease in hair strength rather than an increase.

There may be one explanation for our results, however. Closer inspection of the picture reveals possible

wrinkling on the surface of the hair. This wrinkling could be a sign of shrinkage in the hair. As explored

by Valko et al. [14] and Zviak et al. [15], high pH can result in hair swelling. Bleach is a base and thus

has a high pH. This, along with the rapid dehydration during drying can cause hair to shrink [2]. The

shrinkage can explain increase in hair strength. Our measurement of hair strength looked at the ratio of

hair strength to the tensile strength. Perhaps the tensile strength may have gone down relative to the

original average diameter of the strand, however due to shrinking of the diameter, it seems as if the hair

strength has improved.


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Analysis of reliability and validity of our data

We have already concluded that our data is unreliable and invalid; however we only have qualitative

evidence for this. Quantitative evidence is provided by 2 statistical tests: the 95% CI and a t. test.

95% CI

The 95% CI formulates a range of values where there is a 95% chance a given data point will lie

between. The 95% CI data is shown in Figure 4.2, while it is shown as error bars in Figure 4.3.

We can see huge overlaps of the error bars in the data—this means that there is a chance that two

data points could possibly lay on the same point. This shows that the spread of the data is too

great and that this causes unreliability in our data.

T. Test

The t. test is a type of statistical analysis that tests whether two sets of data are distinct. We will

use the t. test to check whether or not the 1st, 2

nd and 3

rd cycle data are different. If they are not

different, the data states that there is no effect of bleaching cycles on hair strength. The test gives

us a probability value the similarity of the sets. I conducted the T. Test using the average 15

minute hair strength of the 1st, 2

nd and 3

rd cycle. I got a 99% similarity between 1 and 2 cycle and

a 33% similarity between 2 and 3 cycle. Usually, for two sets of data to be considered different

there can only be a 5% similarity. Our three sets can be implied to be samer. Our data is invalid,

inaccurate and unreliable.

Future improvements to ensure valid, reliable quantitative data

Inaccuracy of data

Our flaw was that our data was inaccurate. I hypothesize that this is because of possible shrinking

in the hair, causing our measure of hair strength to be invalid. We should adopt a new method to

measure the hair strength. I suggest that we use Edman and Marti’s [7] 20 per cent index as a

method of hair strength measurement. It requires a 20% elongation of a hair fiber underwater

before and after bleaching. This requires us to have water and to have an elongator. It uses data

from these two stretches to form a ratio and it calculates it as a measurement of hair strength.

Edman and Marti showed results that were accurate and well supported with the use of the 20 per

cent index.

Dry hair vs. Wet hair

Studies by Edman and Marti [7] and Robbins and Scott [12] suggest that a relationship between

bleaching and tensile strength only exists in wet hairs. With an analysis of other hair strength

testing measures, I noticed that most of them were conducted in water [2]. For future experiments,

perhaps tensile strength measurements should be taken with wet hair rather than with dry hair. As

it is not really possible to control for ‘wet’ in our method, going back to alternative methods, it is

probably better to change to a 20 percent index method to find hair strength.


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Storage of hair

At various parts in the data collection period, the hairs were stored in the humidity and

temperature controlled room for long periods of time. With time, dirt was visible on the hairs.

SEM pictures showed dirt on some of the hair strands. Perhaps this could have aided to the

inaccuracy of the data. In the future, we should aim to reduce storage and aim to collect data as

quickly as possible.

More trials

We had 10 trials for every sample. We had a total of 27 samples, resulting in a total of 270 data

points. During the planning, this seemed like a lot however the variation in the hairs, due to

biological variation, couldn’t be accounted for with only 10 trials per sample. Perhaps 25 trials

per sample would be more accurate for data collection.

6. Conclusion Our hypothesis was not supported by our data. Our data showed results that were contradictory to theory

and past studies. We inferred from qualitative analysis (Figure 5.1) that our data was actually inaccurate

and there was visible damage occurring in the hair. This damage would affect hair strength; however this

was not reflected in our data. We further explored the validity and reliability of our data through statistical

tests such as the 95% confidence interval and the t. test. These two tests showed us that our data was

invalid and unreliable, in addition to being inaccurate. The main improvement to this experiment for the

future is to adopt a more accurate technique to measure hair strength. The technique is called 20 percent

index, and works through data generated by elongations of hair strands underwater pre and post bleaching.

Due to our inaccurate data, we weren’t able to conduct as many tests and find out as much information as

we wanted to, however in the future, with a proper hair strength testing method and a few more

improvements, we will be able to produce more precise and accurate data to form conclusions from. In

the future, we should try to research whether or not multiple bleaching cycles have the same effect on hair

strength as a single bleach of the same total time as the cyclic bleaching.

7. Works Cited

Works Cited

[1] M. Bryan, "Howstuffworks "How hair coloring works?"," Howstuffworks, 01 April 2000. [Online].

Available: http://science.howstuffworks.com/innovation/everyday-innovations/hair-coloring.htm.


17

[Accessed 04 February 2014].

[2] C. R. Robbins, Chemical and physical behavior of human hair, 5th ed., London: Springer, 2012.

[3] W. D. James, T. G. Berger and D. M. Elston, Andrews' diseases of the skin: clinical dermatology, 11th

ed., London: Elsevier Health Sciences, 2011.

[4] M. Feughelman, Mechanical properties and structure of A-keratin fibres: wool, human hair and

related fibres, Sydney: UNSW Press, 1997.

[5] R. Barrans, Polloway and M. Rodriguez, "Bleached hair," 1999. [Online]. Available:

http://www.newton.dep.anl.gov/askasci/gen99/gen99504.htm. [Accessed 1 February 2014].

[6] L. J. Wolfram, K. Hall and I. Hui, "The mechanism of hair bleaching," Journal of the society of

cosmetic chemists, vol. 21, pp. 875-900, 1970.

[7] W. W. Edman and M. E. Marti, "Properties of peroxide-bleached hair," Journal of the society of

cosmetic chemists, vol. 12, pp. 133-146, 1961.

[8] C. R. Robbins, "Cuticle damage and the tensile properties of human hair," Journal of the Society of

Cosmetic Chemists, vol. 42, pp. 59-67, 1991.

[9] B. Bhushan, G. Wei and P. Haddad, "Friction and wear studies of human hair and skin," Wear, vol.

259, no. 7-12, pp. 1012-1021, 2005.

[10] J. B. Speakman, "The plasticity of wool," Proceedings of the royal society, vol. 103, pp. 377-396,

1928.

[11] J. Menkart, L. J. Wolfram and I. Mao, "Caucasian hair, Negro hair and wool: similarities and

differences," Journal of the Society of Cosmetic Chemists, vol. 17, pp. 769-787, 1966.

[12] C. R. Robbins and G. V. Scott, "Predcition of dry extension properties of keratin fibers from wet

extension data," Journal of the Society of Cosmetic Chemists, vol. 21, pp. 639-641, 1970.

[13] L. Rebenfeld, H. D. Weigmann and C. Dansizer, "Temperature dependence of the mechanical

properties of human hair in relation to structure," Journal of the Society of Cosmetic Chemists, vol.

17, pp. 525-538, 1966.

[14] E. I. Valco and G. Barnett, "A study of the swelling of hair in mixed aqueous solvents," Journal of the

Society of Coemsetic Chemists, vol. 3, pp. 108-117, 1959.

[15] C. Zviak and J. Rouet, "Melamine and dicyandiamide as depilatory accelerators". US Patent


18

3,217,258, 6 September 1966.

[16] S. S. Funari and L. G. Pinto, "Structural characterization of Asian, Caucasian and African human hair

keratinous fibres," Desy photon science, Hamburg, 2007.

[17] F. Gjesdal, "Investigation on the melanin granules with special consideration of the hair pigment,"

Acta pathologica et microbiologica scandinavica, vol. 47, p. 133, 1959.

[18] "A comparative study of beard and scalp hair," Journal of the Society of Cosmetic Chemists, vol. 34,

pp. 361-368, 1983.

[19] R. Wickett, "Kinetic studies of hair reduction using a single fiber technique," Journal of the Society of

Cosmetic Chemists, vol. 34, pp. 301-316, 1983.

8. Appendix

Appendix A: Switch number and time+cycle information Switch number

Bleaching time

Number of bleaching cycles + comments

1 15 1

2 15 2

3 15 3

4 30 1

5 30 2

6 30 3

7 45 1

8 45 2

9 45 3

10 60 1

11 60 2

12 60 3

13 75 1

14 75 2

15 75 3

16 90 1

17 90 2

18 90 3

19 105 1


19

20 105 2

21 105 3

22 120 1

23 120 2

24 120 3

25 0 0 CONTROL

26 0 0 CONTROL

27 0 0 CONTROL

Appendix B: Raw data Cycle 1 Time (minutes)

0 15 30 45 60 75 90 105 120

Trial 1 1.50 1.58 1.48 1.07 1.02 1.10 0.76 0.92 1.25

2 1.14 1.22 0.94 0.80 0.91 0.96 0.95 1.02 0.76

3 1.27 1.02 0.96 1.06 0.76 0.90 0.79 0.45 0.84

4 0.85 1.01 0.94 1.04 0.82 1.01 0.98 1.01 0.59

5 1.11 0.97 1.23 0.84 0.87 0.93 0.97 0.92 0.68

6 0.69 0.89 1.00 1.13 0.75 0.90 0.99 1.08 0.72

7 1.04 1.29 0.94 1.46 1.31 1.08 1.16 0.66 0.76

8 0.99 0.95 0.91 1.25 0.90 0.96 0.73 0.83 0.89

9 0.92 1.03 1.37 1.15 0.95 0.91 1.24 0.66 0.80

10 1.12 1.10 1.13 0.69 1.06 0.85 1.23 0.62 0.69

Avg 1.06 1.11 1.09 1.05 0.93 0.96 0.98 0.82 0.80

StD 0.23 0.21 0.20 0.23 0.17 0.08 0.19 0.21 0.18

95% CI 0.14 0.13 0.13 0.14 0.10 0.05 0.12 0.13 0.11

Cycle 2 Time (minutes)

0 15 30 45 60 75 90 105 120

Trial 1 0.87 1.47 1.13 1.50 0.99 0.85 0.87 1.00 1.03

2 0.96 0.94 1.47 1.29 0.69 1.12 0.75 0.92 1.05

3 1.09 1.12 1.13 0.96 1.02 1.32 0.88 0.48 0.72

4 0.82 0.79 0.94 1.41 0.82 1.19 0.77 0.64 1.03

5 0.95 1.24 1.13 0.96 1.11 0.92 1.00 0.87 0.98

6 1.10 0.94 1.08 1.12 1.13 1.09 1.18 0.67 0.76

7 1.39 0.97 0.97 0.93 1.22 0.73 0.77 0.99 0.84

8 1.32 1.28 1.14 1.59 1.12 1.05 1.02 0.84 0.80

9 1.19 0.97 1.53 1.23 0.94 0.85 1.17 0.78 0.66

10 1.66 1.36 0.99 1.06 1.58 0.84 0.72 1.00 0.48

Avg 1.14 1.11 1.15 1.21 1.06 1.00 0.91 0.82 0.83

StD 0.26 0.22 0.20 0.24 0.24 0.19 0.17 0.18 0.19

95% CI 0.16 0.14 0.12 0.15 0.15 0.12 0.11 0.11 0.12

Cycle 3 Time (minutes)

0 15 30 45 60 75 90 105 120

Trial 1 1.23 1.15 1.00 1.39 1.10 0.95 0.91 0.85 0.46

2 0.99 0.72 1.03 1.13 1.14 0.81 1.22 0.30 0.84

3 1.34 1.17 0.61 1.28 0.87 1.09 0.75 0.51 0.89

4 1.16 0.72 0.81 1.05 1.33 1.24 1.11 0.78 0.82


20

5 1.46 1.03 0.88 1.17 1.29 0.87 0.03 1.37 0.64

6 0.86 1.04 0.42 1.03 1.01 0.71 1.14 0.78 0.89

7 1.12 1.11 0.99 1.18 1.27 0.33 1.02 1.29 0.94

8 0.85 0.95 0.87 0.89 0.97 1.39 0.86 0.88 0.79

9 1.44 1.04 0.63 1.12 0.78 1.25 0.91 0.99 1.11

10 1.11 1.25 1.05 1.15 0.79 0.71 1.13 1.00 0.56

Avg 1.16 1.02 0.83 1.14 1.05 0.93 0.91 0.87 0.80

StD 0.22 0.18 0.21 0.14 0.20 0.32 0.34 0.32 0.19

95% CI 0.13 0.11 0.13 0.09 0.13 0.20 0.21 0.20 0.12

VINEET YAGNIK BIOLOGY EE

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