How do Mood Pencils Work?

Alyssa Mertes

Alyssa Mertes

Promo Expert

Color-changing items, like mood pencils and cups, alter their appearance with any change in temperature. This occurs by adding either leuco dyes or thermochromic liquid crystals (TLCs) to the product.

Do you remember your high school chemistry class? Chances are if you didn’t fall asleep, you know a little something about molecules and compounds. This basic knowledge is all you need to understand how mood items like rings, pencils, and cups change colors.

How do color-changing promos work? Why do people love these novelty items? It’s time to paint a picture and learn the amazing science behind mood products.

If you’re more of a visual person, watch this interesting video about the color changing process:

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A Brief History of Mood Rings

Without the invention of mood rings, we may have never had other color-changing products. Think of it as one ring to rule them all! The mood ring first came onto the scene in 1975. New York marketing executive Joshua Reynolds was studying biofeedback (electronic monitoring of human body functions), and instead found something new to sell at popular department stores. At the time, the ring wasn’t the cheap plastic version we’ve come to see in souvenir and novelty shops. It was made of real silver or gold and valued between $45 and $250.

These mood rings were an instant success and opened the door for the future of color-changing products. In fact, Reynolds sold $1 million worth in only three months! A string of other color-changing items followed suit, such as pencils, cups, and even clothing. Needless to say, this new phenomenon definitely put everyone in a good mood.


How Do Mood Items Work?

There has to be an extreme change in temperature in order for color-changing items to work. While you shouldn’t throw your mood pencil into a fire or blizzard, you’ll likely see a difference in appearance depending on both temperature and pressure. For example, if you squeeze a mood pencil, it will be a much different color than if you let it sit on your desk.

Of course, temperature isn’t enough to change the color of the product. There are two options for how mood items work.

Leuco Dyes:
The most common method is through leuco dyes. Most promotional products, like mood pencils and stadium cups, use this type of ink to change colors. Each microcapsule inside the dye contains three substances:

1. A colorant
2. An acid
3. A solvent

The solvent remains solid at low temperatures, keeping the colorant and acid close together. As a result, the mixture reflects light and creates color. When the temperature increases, the solvent liquefies and the colorant and acid come apart. At this point the dye becomes translucent, allowing any color, pattern, or word printed on an underlying layer of ink to show through.

What Are Leuco Dyes Used For?
Leuco dyes are found in a wide variety of products. They add a fun element to packaging and typical objects like pens and drinkware. Take a look at some of the surprising places you’ll find leuco dyes.

Thermochromic Liquid Crystals (TLCs)

While they’re not as common as leuco dyes, TLCs are also very effective at changing a product’s color. The crystals are fluid, but their molecules are structured and organized in a way typical of solid materials. This substance is composed of mini capsules that are covered by a chemical base. In warm temperatures (about 80ºF), the capsules reorganize like matches in a box. However, in colder temperatures, the crystals move farther apart. The final color depends on how close the crystals are together and how much white light is reflected.

Thermochromic liquid crystals work very similar to iridescent products. They are also very temperature sensitive, which means they provide a more accurate reading than leuco dyes. As such, they’re used for many important items like thermometers and other medical equipment.

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What Are Thermochromic Liquid Crystals (TLCs) Used For?

Thermochromic liquid crystals (TLCs) are used for a number of essential items. From household appliances to modern technology, check out all of the uses for this substance.

The Bottom Line

Color has a huge influence on every aspect of human life. The taste of the food you eat, your productivity at work, and even the effectiveness of your medication are all impacted by color. With all that said, leuco dyes and thermochromic liquid crystals (TLCs) are welcome additions to the products we know and love. Whether you’re looking for classic mood rings or color-changing floor tiles, these substances are sure to brighten your day!

Alyssa Mertes

Alyssa Mertes

Alyssa is a super cool Copywriter at Quality Logo Products. She’s a fan of diving into the history of some of the earliest promos on the planet. If you need her, you’ll find her buried in research, in the middle of a phone interview, or singing way off-tune in her office.