Gan Eng Seng School Team 1

The comparison of different brands of hairdye and their effects of human hair.

Republic Polytechnic Scientific Thinking Programme 2008

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 ExperimentControlled

VariablesIndependent 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

Tensile strength of each strand of hair

Same dying method used to dye hair for all experiments

MaterialsMaterials Needed:

1. Hair

2. Containers

3. Different brands of hair dye

4. Gloves

5. Microscope

6. 10ml Measuring cylinder

7. Timer

8. Weights and Coins

9. Retort stand

10. Scotch tape

11. Electronic beam balance

12.15-centimetre ruler

13. Scissors

Procedure1. Cut five sets (one set as the control and four sets for the

four different hair dyes) of 10 strands of hair.

2. Hair was dyed 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.

40X Magnification

Results Analysis and Discussion

Average number of hair breaks

0

1

2

3

4

5

6

7

Untreated hair Revlon Hoyu Garnier L’oreal

No

. of

hai

r b

reak

s

Average amount of mass the hair can withstand before breaking

0

20

40

60

80

100

120

Untreated hair Revlon Hoyu Garnier L’oreal

mas

s (g

)

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!