Affordable and readily available, Red Heart is the yarn brand that many knitters, including me, used the first time we picked up a pair of needles. I was surprised to see a pitch from them land in my inbox, as hand-knitting yarn is usually something I don’t get to cover for TechCrunch. But the brand recently released a new line of yarn called Heat Wave, which uses proprietary technology to create acrylic yarn that generates heat when exposed to sunlight.

Like Red Heart’s classic Super Saver yarn, Heat Wave is completely acrylic, but becomes up to 12°F warmer when exposed to the sun, even on overcast days. I learned how to knit on Super Saver and still keep a few skeins in my stash. When I opened the box of Heat Wave samples Red Heart sent me, I found that the yarns felt nearly indistinguishable. I took my skeins of yarn outdoors on a sunny day with an infrared thermometer and found that Heat Wave did indeed measure up to the company’s claims, emitting more heat than either Super Saver or a ball of 100% wool yarn in similar colors.

Amy Olsen, the product development lead of Red Heart, tells me the company worked with a supplier (Red Heart prefers to keep their name under wraps) that developed microscopic acrylic fibers with heat-generating properties in the core. Because it is part of the structure of the fiber, it won’t wash out the way a spray-on application would. The fiber is then spun into Aran-weight yarn at Red Heart’s mill in Albany, Ga.

There are other heat-generating textiles used in commercial products, like Uniqlo’s Heattech line of clothing, but many of them work by retaining heat generated by the body. Because Red Heart Heat Wave absorbs solar energy, it has the benefit of extra warmth when you are outdoors, but returns to the same temperature as other acrylic garments when you go back inside.

As an obsessed knitter and tech reporter, I always get a thrill when these two parts of my life connect. For example, researchers are exploring how to use knitted fabrics in soft robotics, while Georgia Institute Technology mathematician, physicist and hand-knitter Elisabetta Matsumoto is currently conducting a five-year research project to create models that can predict how different types of knitted fabric will behave. On the machine-knitting front, a team of MIT researchers has developed AI-based software that enables people without knitting or design experience to create their own clothes.

Red Heart’s Heat Wave is interesting because it is one of the first times I can recall textile technology used as a selling point for a hand-knitting yarn; hopefully it will encourage more people to explore the intersection between STEM and fiber crafts. Olsen says the yarn will become a regular part of Red Heart’s product line, with plans to release more colors in the future.