Republic Polytechnic Scientific
Thinking Programme 2008
The comparison of different brands
of hairdye and their effects of
human hair.
Gan Eng Seng School Team 1
Aim and Hypothesis
 Aim: To determine which brand of hair dye will
least affect the tensile strength of the human
hair and number of hair breaks found on the
human hair.
 Hypothesis: The more expensive the hair dye, the
better the quality of the ingredients, and hence,
the least it will affect the tensile strength and the
number of breaks on the human hair
About our Hair
 Human hair is made of keratin, water and dead cells
 Each strand of hair is made up of three layers; the Medulla, Cuticle
Cortex.
 Cuticle is made up of scale-like, overlapping protein cells which
protect the cortex
 A healthy hair is when the cuticle lie flat around the hair shaft.
 A damaged hair is when the cuticle of the hair is raised.
http://www.hoyu-usa.com/bigen/abouthair.php
Ingredients of a Permanent Hair Dye
Will usually contain:
Oxidizing Agent
 Will usually be Hydrogen
Peroxide.
 It enters the cortex and
removes some of the melanin
from the cortex layer.
 Lightens the colour of hair,
and also introduces dye
molecules.
Strong Alkali
 Usually Ammonia.
 Ammonia causes
cuticle to swell and
separate
Variables of this Experiment
Controlled
Variables
Independent
variables
Dependent
Variables
Number of strands
of hair used per
experiment
The different
brands of hair dye
Number of breaks
on each strand of
hair after it is dyed
Same length of hair
used for all
experiments
Same dying method
used to dye hair for
all experiments
Tensile strength of
each strand of hair
Materials
Materials Needed:
1. Hair
2. Containers
3. Different brands of hair dye
9. Retort stand
10. Scotch tape
4. Gloves
11. Electronic beam balance
5. Microscope
12.15-centimetre ruler
6. 10ml Measuring cylinder
7. Timer
8. Weights and Coins
13. Scissors
Procedure
1. Cut five sets (one set as the control and four sets for the
four different 40X
hair dyes) of 10 strands of hair.
2. Hair was dyedMagnification
according to the manufacturer’s instruction.
3. When the time is up for all the dyed hair, it is dried and
kept in different containers for easy reference.
4. After the dying process, we checked the number of breaks.
The amount of hair breaks were recorded.
5. Then we hang weights on the hair to test for tensile
strength. They are secured one by one. This was continued
until the hair breaks. The mass that each hair could hold
was recorded.
Results Analysis and Discussion
Average amount
mass the
hair breaks
can withstand
Averageofnumber
of hair
before breaking
7
120
6
100
mass (g)
No. of hair breaks
5
80
4
60
3
40
2
20
1
00
Untreatedhair
hair
Untreated
Revlon
Revlon
Hoyu
Garnier
Garnier
L’oreal
L’oreal
Conclusion
 Dyed hair have a decrease in tensile strength; increase in
hair breaks.
 We conclude, L’Oreal hair dye is the best brand of hair dye
 Our hypothesis (as mentioned earlier) does not stand.
 We found out that there is no relationship between the
tensile strength and the number of breaks on human hair.
Reflections
 Learnt to cross compare and compile the information.
 Able to research smartly and summarize it in our own
words.
 Learnt how to read data and collate them into graphs.
 Such experience equips us with scientific skills that we
can use in future experiments
 Able to interpret raw data into results, and learnt proper
techniques to present these ideas into a scientific report
Thank You!