Thermochromic Color Change Ink
The ink you're looking for is called thermochromic ink. It's a special type of dye that changes color based on temperature.
Thermochromic ink was first invented in the 1930s, but it wasn't until the 1970s that it became widely popular. It was used in mood rings, which changed color based on the wearer's body temperature.
Today, thermochromic ink has a variety of uses. It's used in:
Toys: As with mood rings, some toys use thermochromic ink to create fun and interactive features. For example, a cup might change color when filled with cold liquid.
Packaging: Some companies use thermochromic ink on their packaging to indicate the temperature of a product. For example, a bottle of baby food might change color to indicate that it's too hot.
Security: Thermochromic ink can be used to create security features. For example, a document might have a hidden message that only appears when exposed to heat.
Art: Artists can use thermochromic ink to create unique and interactive works of art.
Thermochromic ink is a versatile product that can be used in a variety of ways. If you're looking for a way to add a touch of magic to your project, thermochromic ink is a great option.