Welcome to STEM Tuesday: Author Interview, a repeating feature for the last Tuesday of every month. Go Science-Tech-Engineering-Math!

Today we’re interviewing Laura Mucha, author of Kaleidoscope: Step into a world of color.

Kaleidoscope paints a vivid and often creepy picture of humankind’s quest to create coloful art materials. The history and science of color is on full display in vivid spreads that highlight specfic colors from indigo to dragon’s blood to vital green. Shocking tales of red candy made with bugs and poisonous wall paper will have kids shouting No way!” and “That’s awful!” and “How cool!” on repeat.

And now, let’s dive into this vibrant interview:

Emily Starr: Let’s start with the shocking: Your final spread shares that a color was made from dead bodies. Wow! How did you discover that information, and what other research surprised you most?

Laura Mucha: I read about it in a general book about color – then to check it actually happened, I found it in Harvard’s Forbes Pigment Collection, which has a tube of Roberson’s ‘Mummy Brown’, plus mummy fragments donated by the firm. I was pretty surprised that artists used paint made from dead human bodies – and I particularly love this paragraph from Kaleidoscope:

Mummy was sold as a paint until quite recently. In 1964, one company stopped selling it because they ran out of mummies, saying, “We might have a few odd limbs lying around somewhere, but not enough to make any more paint.”

I was shocked by how many colors came from bugs, bodily fluids and poison! Some red candies are still colored with crushed insects, Indian yellow was made from the pee of cows fed on mango leaves, and people slathered poisonous lead white on their faces to look their best. But one of the most shocking was Scheele’s green: its inventor knew it was poisonous, but it still ended up covering 100 square miles of British walls and killing people, and no laws were ever made to stop it.

Emily: Allowing poisonous paint to kill people is almost as shocking as the mummies – almost! Like the colors you just mentioned, on each spread, you share specific color names and how those colors are/were created. Are there any colors that didn’t make it in the book that you wish you had space to include?

Laura: My notes ran to nearly 100,000 words, with little comments to myself like “not that interesting?!” I wrote DO NOT INCLUDE next to Amaranth – a pink because the Aztecs reportedly mixed it with human blood to make cakes. (Not ideal for bedtime reading…)

But there were some I really liked that didn’t make the cut because of space. For example, the painter Edward Burne-Jones, who buried his tube of mummy brown in the garden when he found out what was in it. Or the Indian artists who used shiny beetle wings for the emeralds in their paintings. I cut other things to avoid repetition: why the sky and sea are blue, for example, is really about light, which I covered elsewhere in the book. Every spread was a fight over which brilliant fact got the space.

Gray, gold, and silver all nearly got spreads of their own – silver has wars, currencies, and even a country named after it (Argentina comes from the Latin for silver). But in the end gold made an appearance and silver and gray didn’t – a decision I still agonize over.

Emily: Your examples span a long timeline and include the use of color in different cultures. Did this require you to consult with experts? If so, can you talk a little about that process?

Laura: I researched the book using books and articles written by experts, doing a HUGE amount of fact-checking, and going to experts when I needed to. I kept doing rounds of fact checks and was frustrated to find major errors in books by reputable authors, published by top publishers. (One told me Neanderthals made violet 25,000 years ago – which would have been tricky, given they’d almost certainly died out some 15,000 years earlier!)

I think color is especially hard to write about accurately because it belongs to chemists, archaeologists, art historians and textile specialists, and they don’t always read each other’s work. So where experts disagreed and I couldn’t resolve it, I didn’t include the information.

Where something was too important to lose, I asked someone. Two of those people are in the acknowledgments: Aviâja Rosing Jakobsen, Curator at the Greenland National Museum and Archives, who helped me check that what I was saying about West Greenlandic national dress was accurate (which I couldn’t verify from books), and Dr. Ruth Siddall, who helped me get to the bottom of a very niche question about cave art.

I also relied on the young reviewers, who are in the acknowledgments too – they told me if an explanation hadn’t actually worked (or was boring!).

Emily: Throughout the book, you mention environmental concerns–especially for animals that are killed to produce specific colors. How do you personally think about balancing the desire for pigments (and the reality that we know more today than in the past) with the need to protect our natural resources?

Laura: Humans have gone to extremely destructive and sometimes dangerous lengths to create color.

Making Tyrian purple usually meant smashing the shell of every snail, leaving rotting heaps piled up along shores. But people in Nicaragua found another way: squeeze out the mucus and put the snail back. So the damage didn’t have to happen – but most people smashed the shells anyway. Damage is usually the cheaper option, chosen by people who won’t be the ones to pay for it – the snails, the miners, the elephants.

I don’t think the answer is to want less color. I’d never ask a child to feel guilty for loving it – people 17,000 years ago walked three miles to make black from manganese when there was perfectly good charcoal by the fire. The question is what we’re willing to pay, and who does the paying. What’s genuinely different now is that we can see the bill – and we have more ways to avoid it, from a lilac color grown from bacteria to dyes made from algae.

Emily: You include many examples of colors that are dangerous or deadly. Do you know if any of those colors are still in use, and if so, why? What precautions are taken? After reading your book, I’m going to steer clear of all pea green wall paper! (Shouldn’t people avoid plastering pea green all over their walls anyway?! Ha!)

Laura: Pea green walls are safe these days – whether they’re stylish or not is another matter…

The arsenic wallpapers are gone. But lead is not. According to the World Health Organization, as of January 2024 only 48% of countries had any law controlling lead paint. It’s still legally made and sold in much of the world. Some of the book’s toxic colors are still made for artists, too. You can buy real vermilion and lead white from specialist suppliers, but they come with warning labels, and there are safer look-alikes. They’re still made because the dangerous colors are often excellent performers – for example, lead white stays flexible and resists cracking.

But people and countries disagree on how dangerous something is. For example, the European Union stopped allowing titanium dioxide in food in 2022 because its food safety authority couldn’t rule out that it damaged DNA. Whereas Great Britain, the US, Canada, Australia and New Zealand looked at the same evidence and have kept it (so far). So, depending on where a candy is sold, the same white coating is either allowed or banned.

Emily: Given that reality, is there a resource you recommend for readers who want to investigate how the colors in their everyday lives are currently produced?

Laura: There’s no one-stop shop. The information is scattered across food regulators, textile certifiers, conservation scientists and paint manufacturers. But here are some good places to start.

Harvard Art Museums’ Forbes Pigment Collection holds more than 2,500 pigments, with a free online audio tour through twenty-seven of them, from charcoal to YInMn blue (harvardartmuseums.org/tour/660). The mummy brown tube lives in that collection.

The FDA also has a guide to the colors in your food: fda.gov/food/color-additives-information-consumers/color-additives-questions-and-answers-consumers The best thing to do when it comes to food is read the ingredients list, though not every color has to be named (titanium dioxide, for instance, can appear on US labels simply as “artificial color”). In the US, look for “carmine” or “cochineal extract” on the label; in Europe and the UK, it’s often listed as E120. It’s crushed insects, it’s in the book, and it’s probably in something that you have in your kitchen.

Emily: This is the perfect STEAM book for all classrooms! You artfully show how science and art are inextricably linked. I instantly thought of Next Generation Science Standards connections in kindergarten, fourth grade, fifth grade and middle school.  How do you recommend educators use your book with students?

Laura: Thank you so much for your kind words!

For kindergarten, K-ESS3-3 asks children to communicate solutions that reduce human impact on the local environment. The Tyrian purple spread (pp. 44–45) gives children two ways to get the same color: smash the shell and kill the snail, or squeeze out the mucus and put it back in the sea. Ask five-year-olds which is better, and why – and to explain it to someone else. Then ask what “squeeze” or “smash” would look like where they live.

For fourth grade, 4-PS4-2 is about modeling how light reflects off an object and into the eye. The goldfish spread (pp. 14–15) is exactly that.

For fifth grade, 5-PS1-1 asks for a model of matter being made of particles too small to see. Gamboge (pp. 20–21) gives them the evidence: a physicist watched tiny yellow grains darting about in a way that only made sense if invisible particles were knocking into them, and it won him a Nobel Prize. And for 5-PS1-4, the reaction spreads are everywhere: copper turning green, iron turning red, lead and vinegar turning white in a clay pot packed in animal dung in a shed… The copper and iron ones are easy to try in class (vinegar-soaked pennies, damp steel wool) – just not the lead one!

For middle school, MS-PS4-2 is about light being reflected, absorbed or transmitted depending on the material. Kaleidoscope has two examples where structure, not pigment, decides what happens to light: Vantablack absorbing almost all visible light (99.965 percent) – and then the blue morpho butterfly, which is blue purely because of the shape of its scales (it has no blue pigment). Both make one of the NGSS crosscutting concepts visible: structure and function.

But if I could get teachers to use one spread at any age, it would be the cave art spread (pp. 10–11): young María finds the paintings, an important expert in prehistory declares them fake without ever going to the cave, most experts believe him for years, he eventually admits he was wrong and apologizes to her – but he’s too late to apologize to her father, who has died. It’s a case study in how science actually works: experts can be wrong and being willing to say so is essential. Having discovered, while writing this book, how many confidently stated facts about color don’t survive checking, I’d love every child to learn this lesson!

Another theme throughout the book is that science and art were never really separate subjects. Colors are often a chemistry problem someone solved because they wanted to make something beautiful.

Photographer: Rii Schroer

Laura Mucha is an ex-lawyer turned award-winning poet and Author-in-Residence in the Department of Public Health & Primary Care, University of Cambridge. Her writing has won multiple international awards and been featured on TV, radio and public transport, as well as in hospitals, hospices, prisons, books, magazines and newspapers around the world.Last year, as well as judging the British Book Awards, she broke the Guinness World Records title for Largest Poetry Lesson (multi venue) together with 43,516 young people from over 500 schools around the world. The year before, her book Welcome to Our Table won Children’s Book of the Year 2024: Non-Fiction (The Week Junior) and she was the runner up for the Ruth Rendell Award for the author who’s had the most significant influence on literacy in the UK over the past year. When not writing, Laura spends her time visiting schools around the world and working with organizations such as the Royal Society of Medicine, National Literacy Trust, Centre for Literacy in Primary Education, and UNICEF to try to improve the lives of children.