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The Science Behind Dyeing My Hair (with cool pics!)

April 26, 2023

Ten years ago, if you told me that I was going to dye my hair red when I was 21 years old, I would have told you that you were absolutely lying! I would never (according to 11-year-old me). But according to 22 year old me, yes — I absolutely did dye my hair red, and it’s here to stay for the next few years because I absolutely love it!

The first time I dyed my hair, it was in the Fall of 2022. I wanted a big change (for personal reasons I will not delve into), but I wanted to do something I never did before. Something that will make me feel new. It did not come for cheap, however. It was worth it nonetheless. This lovely thing I’m talking about is hair dyeing!!

So, what exactly goes behind hair dyeing? It all boils down to chemistry! The process is different depending on the type of hair dye you get: temporary/semi-permanent, demi-permanent, and permanent. Since I decided to get permanent red hair dye, I will discuss about the permanent hair dye process. Permanent color is what is needed for a more significant hair color change (i.e. from black to red or blond).

Your natural hair color depends on the quantities and ratios of 2 main proteins: phaeomelanin and eumelanin. Eumelanin causes hair to be brown or black while phaeomelanin causes hair to be blond and red shades. My hair is jet black, so that means my hair is mostly composed of eumelanin.

My natural hair color –> jet black.

Both ammonia and hydrogen peroxide are used. Ammonia and peroxide act to lighten the hair’s natural color to form a new base color that will allow the permanent hair dye to stay.

The cuticle, or outer layer, or the hair strand must be opened before permanent hair color can be applied into the hair. Once the cuticle is open, the dye reacts with the cortex of the hair to deposit or remove color. The cortex is the part of the hair that is the middle layer of the hair shaft which provides the strength, color and texture of a hair strand. There is usually a two-step process for permanent hair coloring: first to remove the original color of the hair, and then the second to apply a new color. 

The anatomy of a hair strand.

The alkaline chemical of ammonia is used to open the cuticle to allow the hair color to enter the cortex of the hair. Additionally, it is a catalyst when the permanent hair color combines with the peroxide. Hydrogen peroxide is used as an oxidizing agent, or a developer to remove pre-existing color (it removes the melanin in the hair). Peroxide breaks chemical bonds in the hair, which releases sulfur. This is why there is such a strong odor when dying hair. As the melanin is removed from the hair, the new permanent color is bonded to the cortex of the hair. 

The result of hydrogen peroxide on my hair (to lighten it)!

And voila! The hair dresser then washes your hair and styles it. I opted for a haircut and a blowout hairstyle. Shoutout to my talented hairdresser Christi at Cherry Blossom Salon! 

Finished product!! I’m still so in love

Have you ever wondered what dyed hair vs non-dyed hair looks like under a microscope?

Well look no further! With the help of Dr. Leavey, a classmate and I were able to look under the microscope of the molecules of our hair. The picture on the left is mine (red dyed hair) and the one on the right is my peer Claire’s hair (undyed black hair). As you can see, my hair cuticle and cortex are much more jagged and rough, compared to Claire’s smooth strand. This is a result of the chemical reactions that occurred to my hair – the ammonia and peroxide chemically and physically damaged my hair to allow the red color to deposit into my strands.

My red dyed hair.
Claire’s undyed black hair.

 

What is wild is that my dyed hair is essentially permanently damaged. I will have to grow out my original black hair if I want to revert back to my undamaged hair. For now, I think I will stick with damaged dyed hair! 🙂

 

 

 

 

Sources:

Anne Marie Helmenstine, P. D. (2019, July 14). The science behind how hair coloring works. ThoughtCo. Retrieved April 26, 2023, from https://www.thoughtco.com/salon-hair-color-chemistry-602183

Brain, M. (2023, March 8). How hair coloring works. HowStuffWorks Science. Retrieved April 26, 2023, from https://science.howstuffworks.com/innovation/everyday-innovations/hair-coloring3.htm

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About Author

Devi is an undergraduate at Georgia Tech studying computer science. In her free time, she enjoys jogging, cooking and baking new things, jamming to vinyls and music, and gazing at the stars. Devi also loves cats!! (meow)

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  Timothy Durham was convicted of rape when a test showed his DNA genotype matched the DNA recovered from the crime scene. Eye witnesses testified that Durham was in a different state at the time of the incident, but he wasn’t exonerated from his 3000 year sentence until follow up DNA analysis showed that the preliminary forensic analysis used in the trial was misinterpreted (Thomas et al.). DNA testing serves an invaluable part in our criminal justice system, but it comes with complications and bias that can lead to wrongful convictions and misinformed juries.  

Background:

Forensic genetics aims to identify the origin of a biological sample. It can be traced back to Karl Landsteiner who discovered human ABO blood groups. With blood groups, suspects could be eliminated based on their blood type. For example, if a suspect had type A blood and there was type B blood left at the scene by the perpetrator, the investigators could rule out the suspect. Unfortunately, the reverse didn’t work. If the suspect and perpetrator both had the same blood type, it can’t be concluded that the suspect was guilty. Blood identifiers evolved into 8 distinct categories which improved the ability to eliminate suspects, but could only conclude that (if the system matched) it might be the perpetrator or this person might be related to the perpetrator (Jobling and Gill). The field evolved in the 1980s with the discovery of Minisatellites, lines of repetitive DNA that don’t encode proteins. Minisatellite patterns in DNA create what we know today as the DNA fingerprint, and it has a much higher accuracy rate than previous methods (Augustyn et al.). Around the same time, a breakthrough for victims of sexual assault was discovered. In the case of assault, bodily fluids of both the victim and the assaulter can get mixed. A process called differential lysis was created which could selectively increase the concentration of sperm in a fluid sample thereby allowing for accurate DNA testing (Jobling and Gill). Forensics evolved to use single-locus probe testing after several years because of its ease of interpretation. It looked at specific minisatellites that had high variability between subjects. This was the first DNA-based method to be used in a criminal investigation. Two murder homicides from several years apart were connected using DNA evidence. The evidence was then used to exonerate an innocent man, and the guilty party was found when he tried to evade mandatory DNA testing for all men in the small town. His guilt was then reinforced when the DNA profiles matched, and he gave a confession (Jobling and Gill). Finding DNA at a crime scene doesn’t guarantee that you’ll find a murderer. There are issues with non-pure samples and limited samples that make DNA work difficult, and accreditation of facilities and new techniques and take time (Jobling and Gill).  

Subjectivity of DNA Interpretation:

In a 2009 publication, the National Academy of Science discusses the possibility for subjective influence in lab based forensics. The interpretation bias happens in complex cases where, for example, there could be a mixture of DNA. A study published in 2011 looked specifically at this issue. A gang rape happened in Georgia, and the mixture in DNA from the case was used to prosecute one suspect after another suspect took a plea bargain to testify against him. With DNA mixtures, there are three possible conclusions: suspect excluded, suspect cannot be excluded, and inconclusive. If the suspect is excluded, it means that there’s little to no possibility that his DNA is part of the sample. If the suspect cannot be excluded, it means that there’s a possibility that his DNA is part of the sample. In the trial, the DNA examiners who knew the context of the case concluded that the suspect being prosecuted could not be excluded. The 2011 study gave the DNA evidence from this case and the DNA profiles of the suspects to 17 forensic examiners. These examiners had no context of the case, and they all worked independently. Of the 17, only 1 came to the same conclusion (suspect cannot be excluded) as the examiners who knew the context of the case. Twelve of the 17 concluded that the suspect who was prosecuted and convicted had no relation to the DNA found in the sample. Not only does this show that subjectivity occurs due to the context of the case, but the 17 examiners came up with different findings based on their past experiences meaning that not all DNA analysis is objective. Some organizations like the Scientific Working Group on DNA Analysis Methods say that quantitative statistical evidence should be presented with every categorical conclusion, but the US doesn’t require this (Dror and Hampikian).

False Positives:

There are two categories that cause wrongful identification in a DNA report: coincidental matches and false positives. Coincidental matches are DNA matches between two unrelated people. The probability of these matches is about 1 to 500,000 for white individuals and about 1 to 350,000 for black individuals. This small probability of coincidental matches makes people feel confident in DNA evidence. False positives, on the other hand, are matches between DNA and test DNA that result from issues in the forensics lab. There have been multiple cases of forensics labs accidentally switching victim and suspected rapist DNA which lead to convictions that were later overturned when the lab realized the error. There are also cases of misreading or misunderstanding a sample. In a case from 1993, a man was convicted of rape because someone interpreted a mixed sample of victim and perpetrator DNA as an individual sample. The conviction was again overturned. To prevent false convictions, retesting DNA is allowed, but it’s not an efficient solution. Many people are pushing for statistical information on the probability of false positives, so that the jurors can make accurate judgements based on DNA evidence (Thomas et al.).  

Conclusion:

DNA analysis is a useful tool for the criminal justice system, but subjectivity can be an issue in forensic testing. To combat wrongful convictions, there are organizations like The Innocence Project who use DNA testing to free the innocent, but reformed forensic testing standards should be put in place to prevent subjectivity and to ensure juries are correctly informed during trials. https://www.innocenceproject.org/    

Citation:

Augustyn , Adam, et al. “DNA Finerprinting.” Encyclopedia Britannica , 26 Apr. 2018, www.britannica.com/science/DNA-fingerprinting#ref153186. Dror, Itiel E., and Greg Hampikian. “Subjectivity and Bias in Forensic DNA Mixture Interpretation.” Science & Justice, vol. 51, no. 4, 2011, pp. 204–208., doi:10.1016/j.scijus.2011.08.004. Jobling, Mark A., and Peter Gill. “Encoded Evidence: DNA in Forensic Analysis.” Nature Reviews: Genetics, vol. 5, no. 10, Oct. 2004, pp. 739–751., doi:10.1038/nrg1455. Thompson, William C, et al. “How the Probability of a False Positive Affects the Value of DNA Evidence.” Journal of Forensic Sciences, vol. 48, no. 1, Jan. 2003, pp. 1–8., doi:10.1520/jfs2001171.