What Are Hypercolor Shirts And How Do They Work?

"The Matrix" isn't the only thing from the '90s being resurrected. Those who grew up in the grunge era can dredge up the animal prints and "mom jeans" from the back of their closet and call it vintage fashion, but one '90s trend that hasn't broken back into the fashion scene in recent years is hypercolor T-shirts. (Although you can still find them on Etsy.)

For Gen Z and Millennials who don't remember these shirts, they work similarly to mood-rings, changing colors with heat in a process called thermochromism. If you couldn't decide whether to wear a purple or a pink top while getting ready in the morning, you could pick out your hypercolor T-shirt and have the best of both worlds. They were relatively cheap at $20 a pop, and the technology powering them was also used to make shorts, pants, sweatshirts, and tights (via Smithsonian Magazine). Things could get awkward if your armpits started to sweat in these shirts, but the cool neon colors they came in were worth the embarrassment.

Hypercolor fabric gets its color-changing power from a chemical reaction, which uses two types of dye that allow for color changes. First, the fabric is dyed the "true" color, with the absence of heat. Then, the fabric goes through another round of "leuco dye," which is typically composed of a weak acid and a dissociable salt dissolved in a fatty alcohol (per Mental Floss). These dyes can become any color but are colorless at low temperatures. With heat, the salt dissolves, lowering the pH and the process reveals the leuco dye's color. That's a scientific way to explain that the molecules in the dye "changed shape and shifted from absorbing light to releasing it, making the color transform," according to Smithsonian Magazine.

This same process is used in Duracell batteries to indicate which way energy flows through them. It sounds like a futuristic idea that you could imagine making a comeback today, but it was 1991 when Generra, a Seattle-based company, put hypercolor shirts on the market. 

They managed to sell $50 million worth of products in just three months, per Smithsonian Magazine.  However, owners of these shirts may remember they often lost their color-changing powers after a hot wash or two, and eventually turned into a muted color. In 1992, Generra declared bankruptcy because the company got too big too fast (via Smithsonian). Turns out the trend faded over time — just like the shirts.