How Does Hair Dye Work?

Recently I was home visitinshutterstock_384171025g my family and I noticed something about my mom I had not paid attention to before – her hair…was turning grey.  Now usually my mom gets her hair professionally colored before any of those sneaky grey hairs start to peak through, but sometimes life gets a little hectic. And with time, everyone’s hair will turn grey, so my mom isn’t alone. Luckily there are a variety of options to combat this unavoidable part of life – one being hair dye. But have you ever stopped to consider how hair color really works?    

*Before I go any further I would like to apologize to my mom. I’m sorry I noticed your hair was turning grey and am taking advantage of it to write this blog post.But these are the things curious people like me do in the name of cool science. So, now that I’ve gotten that off my chest, let’s talk about why this happens and what we can do about it.*

There are several types of hair color you can use, but we will focus on explaining two of the more common types — temporary and permanent hair color.

Temporary Hair Color

Just as the name implies, temporary hair color isn’t meant to last a long time. Temporary hair color is a large molecule, and when applied coats the outside of the hair shaft, rather than the color penetrating the cuticle. Temporary hair color does not contain ammonia, which is found in permanent hair colors – we’ll talk about that next, though. In addition, this type of hair color doesn’t contain harsh chemicals, meaning you don’t have to worry about damaging your luscious locks. Temporary hair color will only last for a handful of shampoos, so it’s perfect for testing out a new hair color or last minute touch-ups.

Permanent Hair Color

Permanent hair color is the right decision for someone wanting to make a significant color change. With this type of hair dye, ammonia and peroxide are used. Ammonia is an alkaline chemical that helps open up the hair shaft for the color to be deposited on the hair. According to About Education, “peroxide is used as a developer or oxidizing agent. The developer removed the pre-existing color.” Small molecules enter the cortex and upon reaction, they expand to a size that cannot be washed out. Typically, applying permanent hair color is a two-step process. First, the original hair color is removed, and then the new color is deposited; leaving your hair with a fresh glow that lasts, but requiring touch-ups as your hair grows out.

Hair coloring has grown in popularity over time. In 1950, it’s estimated only seven percent of women colored their hair. In 2015, that number jumped to 70 percent. And while aging and greying hair aren’t topics anyone likes to bring up,it’s a fact of life and we have to embrace it! Who knows, maybe with time you’ll learn to rock grey hair just like George Clooney.

2 Comments


  1. Wonderful post. It’s always good to know about the history of hair dye.

    Reply

    1. Hi Terry,

      Thanks for reading our blog! We love sharing everyday science with our audience – Stay curious!

      Best wishes,
      Ashlyn Davidson
      Polymer Solutions

      Reply

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