You (or your parents) may remember the original color-changing shirts; they were first marketed in 1991, and were extremely popular; the company that made them sold $50 million in just three months! Your shirt is the modern descendent of those first color-changing pioneers, and can handle washing and daily treatment like they never could.

How do the shirts work? It’s a fascinating combination of chemistry and textile engineering. The first secret is that there are actually two separate dyes in the shirt - a “base” dye (in this case, yellow) and a heat-sensitive leuco dye (in this case, blue). The heat-sensitive dye is contained in tiny microcapsules, along with a weak acid and a salt that’s dissolved in a fatty alcohol called 1-Dodecanol. When exposed to heat, the fatty alcohol dissolves, releasing the salt, which reacts with the dyes and causes them to change color.

Leuco dyes can either start clear and change to a color when warmed, or start as a color and change to clear. For your shirt, when it’s cooler the dye is blue, combining with the yellow base dye to make a green shirt. As the shirt heats up, the blue dye turns clear, showing the yellow base dye underneath. The change generally occurs at around 29ºC (84ºF).

Studies have shown that using thermochromic paints based on that same technology could save billions of dollars every year. How? Through energy conservation, using paint that turns dark in the winter (absorbing light) and light in the summer (reflecting it), in order to increase the efficiency of heating and cooling. Scientists have found it’s possible to save almost 51% of heating and cooling costs by painting a building with thermochromic paints; doing so made the buildings 11ºC (20ºF) cooler in summer and 2.7ºC (5ºF) warmer in the winter! And more than just paint, researchers are studying how to make the entire building - the concrete, the windows, even the asphalt on the road outside - similarly color-changing, for even more savings. We may one day live in cities that look different depending on whether it’s warm or cold outside.

Thermocromic tech could also save more than 3,000 lives annually in the US alone! Each year, spoiled food causes 3,000 deaths, 78 million illnesses, and $6.5 billion in medical expenses. So the US Department of Agriculture has sponsored promising research into “smart packaging” - thermochromic labels that would show people if the food they buy had ever been heated to the point where bacteria or other pathogens might be present, alerting customers that the perishables inside could make them sick.

Thermochromism can also be found in nature, including among that most desired of gemstones: the diamond. “Chameleon diamonds” are an extremely rare form of carbon that changes color when exposed to heat - around 150°C (302°F). And just like your shirt, chameleon diamonds change from green to yellow. Because of their rarity, chameleons are also extremely expensive, roughly twice the price per carat of a beautiful “normal” diamond, routinely fetching $20,000 USD or more for just .2 grams of stone.

We can’t promise that your shirt is worth twice its weight in diamonds, but we can say it’s a lot of fun, and the shifting designs are always intriguing. So get out there and let your colors shine! And shift.

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