How do Mood Pencils Work?

Alyssa Mertes

Alyssa Mertes

Promo Expert

With so many people enjoying color-changing mood items—you could say they have a certain "chemistry." But did you know when you witness the colors changing, you're actually seeing chemistry in action? Learn about the amazing science behind how mood items work with this article!

Everyone loves a good product with a fun gimmick. Whether it's a stress ball that talks to you or a pair of glasses that glow in the dark, a product that gets people to interact with it beyond its initial use is an advertising gold mine, not to mention a good way to keep the kids entertained at parties. (Not to mention a good way to keep the adults entertained while they're stuck in their cubicles.)

One of our favorite goofy products is the mood pencil. Color-changing items like this one have been in play since the 1970s, when the first mood rings began sweeping jewelry stores and discos across the nation. (We're actually not sure about the disco part; we're just basing that on our parents' embarrassing old photos. Nice hair, Mom.)

Since then, color-changing inks, papers, and paints have been developed for use in all sorts of products. These include some of the items you'll find on the Quality Logo Products site (like mood pencils, pens, mugs, and tumblers), as well as other items you use regularly (like thermometers, battery chargers, and Hypercolor t-shirts if you're a child of the early '90s).

Thermochromatic Liquid Crystals: TLC for Your Items

But how do mood items work? Well, it depends on the kind of ink they use.

Mood items are thermochromic items, which is a fancy way of saying they change color with changes in temperature. For the most part, there are two different kinds of substances that manufacturers use to make thermochromic goods.

The first are pigments that contain thermochromatic liquid crystals, which we'll shorten to TLCs because we love them. TLCs have some properties of liquids and some properties of solid crystals. They're fluid, but their molecules are really structured and organized, which is what you'd expect from a solid.

To make the pigment, the TLCs are microencapsulated, which means they're put into really, really tiny capsules, so small you can't naturally see them. This keeps the crystals from being damaged. The capsules then are floated in a chemical base.

When TLCs are exposed to warmer temperatures (around 27-30 degrees Celsius, or 80-86 degrees Fahrenheit), they reorganize and reposition themselves so they reflect light differently. We can't see it happening, of course, but what we do see is a change in color!

Let’s Set The Mood...

TLCs are very temperature-sensitive (as well as being sensitive to UV light and certain chemicals), so they're a little tricky to work with. However, that sensitivity makes them accurate temperature gauges, and that makes them good for use in products like medical thermometers, aquariums, and, refrigerators. They're also used in mood rings, because why not?

Leuco Dyes: They're Dye-namite!

When it comes to manufacturing budget products in bulk, there's another option that works at a much greater temperature range than TLCs do: leuco dyes.

Leuco dyes are a little bit like TLCs in that both contain microencapsulated particles. Whee, little capsules! In the case of a leuco dye, the capsules contain three substances:

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

At low temperatures, the solvent is solid, and the three types of particles hang out close together and reflect light, which tells the human eye, "Hey, there's a certain color here!" As the temperature rises, the solvent liquifies, letting the particles flow willy-nilly. The leuco dye becomes translucent, allowing the color of the material underneath to show through.

Because they work over a wide range of temperatures, leuco dyes are used in a lot of common items – or in a lot of items for special occasions, like the ever-cherished stadium cup. They're also used in a few printing processes, including offset lithography and our favorite, screen printing.

Whether they are referred to as thermochromic or mood items, color-changing products are a really fun promotional giveaway. They also work in a couple of different ways, as seen above. The variety you get with color-changing items reflects the different ways you can customize your promotional merchandise. That's something we figure is sure to put you and your customers in a good mood!