LLM (google/gemini-3.1-flash-lite-20260507) summary:
- Academic Obsession: a student prioritizes chemistry as a core identity feature while attempting to force enthusiasm upon an indifferent public through outreach programs.
- Outreach Participation: the chemistry group organized a booth at a public festival to showcase material chemistry through amateur demonstrations.
- Pigment Application: body paint was formulated by mixing powdered turmeric into a white base to create temporary yellow decorative designs.
- Accidental Discovery: the yellow pigment vanished after brief exposure to sunlight, prompting a trivial investigation into the underlying causes of the fading.
- Curcuminoid Properties: scientific literature is referenced to highlight the structural attributes and purported biological benefits of common kitchen additives.
- Photodegradation Mechanism: ultraviolet light triggers the breakdown of complex molecular structures when exposed to ambient environment factors like air and sun.
- Structural Transformation: the complex curcumin molecule splinters into simpler fragments like vanillin, which inherently alters its light-absorbing and reflective capabilities.
- Instructional Utility: the simple phenomenon of dye degradation is promoted as a profound insight for organizing household spice storage in dark cabinets.
As you could probably tell by spending two minutes in my presence, I love chemistry. It’s part of who I am. To some people, that might get a little annoying, but I promise I know to tone down the chemistry nerdiness depending on my audience. While learning the technical information is great and all, what really excites me is seeing chemistry in action, especially when it catches me by surprise.
Because I’m such a chemistry enthusiast, I have made it my mission to convince people that chemistry could be fun (I know, not exactly an easy task). Naturally, this has made me gravitate towards science education initiatives such as the OSS and the McGill Chemistry Outreach group. Through these experiences I have been able to nurture my love of teaching all while satisfying my overcurious mind. But what I really want to talk about here is a moment that made me fall in love with chemistry all over again.
Love at first light
This past week, I coordinated the Chemistry Outreach Group’s participation in Eureka fest. Every year this festival brings together organizations from across Montreal to share science with the public through hands-on activities and demonstrations. This year, our group put together an impressive tent featuring demonstrations that showcased materials chemistry at its finest (no bias, of course).
One of these demos involved making body paint, using various extracts of dyes and pigments. Among them was curcumin, the compound responsible for giving turmeric its vibrant yellow colour. To make our paint we added some of this powdered spice to a white face paint base and mixed until smooth. As expected, the curcumin paint would go on the skin a beautiful bright yellow. This obviously prompted all of us demonstrators to decorate ourselves with matching sun-shaped tattoos.
But after a quick walk in the sun, something unexpected happened.
My colleagues went to check out some of the other booths, but when they returned holding out their arms, I was intrigued. I went over to them only to see that their previously yellow tattoos, had turned white. At that moment, this article practically wrote itself.
Getting to know turmeric
We all know turmeric in a kitchen setting. Whether you’re adding it to enhance the flavour of your curry or even in your ginger “wellness” shots, its smell and colour are very familiar. But what we don’t think of often, is its chemistry.
Curcuminoids are the family of compounds responsible for both turmeric’s vibrant colour and biological activity, the major one being curcumin. Because of their structure, these curcuminoids are potent antioxidants. Their phenolic rings (those polyphenols Dr. Joe talks about so often) are able to neutralize those nasty free radicals and protect our cells from oxidative stress. Also, there is some evidence that turmeric can be used to manage certain inflammatory conditions, but it’s not a miracle worker. Anyways, I’m not here to teach you how to cook or eat, I am here to answer the question: why did our tattoos turn white?
Photodegradation
After looking into this, the answer to my question is relatively simple. Curcumin is UV sensitive. When exposed to the rays of the sun for long periods of time, it starts to degrade by a process known as photodegradation. As the name suggests, this process refers to a change in a material by light. This change is usually triggered by the combined effects of sunlight and air which can cause compounds to break down. We’re not talking about a chemical breakdown due to heat; we’re really talking about degradation throughout the ultraviolet spectrum.
In the case of our turmeric tattoos, exposing them to the sunlight during our walk, triggered photodegradation, causing the curcuminoids to breakdown into smaller phenolic fragments like vanillin (the compound responsible for vanilla flavour). This breakdown is responsible for the colour fading. The original structure of curcumin is long and complex and has the ability to absorb blue-violet light, thus reflecting yellow light (by the principle of complementary colours). When we disrupt this structure, the molecule can no longer absorb light in the same way, causing the colour to fade dramatically.
At this point, you may be wondering what this has to do with your everyday life. As it turns out, understanding turmeric’s chemistry can be surprisingly useful when it comes to organizing your spice cabinet. You probably already sore it away from direct sunlight, but now you know why.
Love actually is all around
So, there you have it, we unintentionally made colour-changing tattoos, and to me that’s the wonder of chemistry. The smallest observations can inspire fascinating questions and unexpected lessons. This experience reminded me why I fell in love with chemistry in the first place, and just how interesting the world becomes when you’re willing to be curious. My friends often say I ask too many questions, I think it’s part of how we learn. Stay curious.
Angelina Lapalme is a U3 BSc student majoring in Bio-Organic Chemistry at McGill University.
Part of the OSS mandate is to foster science communication and critical thinking in our students and the public. We hope you enjoy these pieces from our Student Contributors and welcome any feedback you may have!
Cummings during his time in Downing Street. (Isabel Infantes/AFP via Getty Images)