1. 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

2. 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

3. 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

4. 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

5. 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 Tensile strength of each strand of hair Same dying method used to dye hair for all experiments

6. Materials Materials 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

7. Procedure 1.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

8. Results Analysis and Discussion

9. 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.

10. 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

11. Thank You!