How your cooling towel works

 The Cool Nature of Evaporative Towels

Cooling towels are a low-maintenance item that can help keep you cool or even avoid medical problems while you're out riding. How do they work though? Why do they feel so weird and yet so cold? Let's find this out together!

What is a cooling towel and how do they work?

A cooling towel is a towel made up of synthetic materials that are designed to hold large amounts of water and help create a cooling sensation on the skin as the water evaporates. After dampening the cloth it creates a chilling feeling. Cooling towels are generally made from a hygroscopic (likes water) synthetic material (PVA) or a microfiber-like mesh fabric. The PVA ones are very cardboard and stiff when dry but turn into a spongy almost rubbery feeling material when wet. 

Evaporative Technology Cooling PPE - Pryme

Microfiber feels like a soft light fabric if it's wet or dry. 

Evaporative Technology Cooling PPE - Pryme

How they work is through a concept called "evaporative cooling."  This is a descriptive way of describing how things feel cold when water evaporates into the air, exactly how sweating works for our skin. Because these fabrics and materials can hold onto a lot of water they can allow for a lot of evaporative cooling to occur. 

How Does Evaporative Cooling Work?

When a substance changes its phase (Solid > Liquid > Gas) it takes a certain amount of energy to do it. It will absorb this energy from around itself to be able to change the phase of itself. This is why ice feels cold, it absorbs the heat from around it to give it the energy to change its phase. It's also why as water freezes it will slightly increase in temperature to give away that energy needed to solidify itself. 

"When water freezes and ice crystals form, there is actually a small amount of heat produced. The temperature of the water remains at 32°F as the ice crystals grow, and then a rapid temperature drop occurs as the ice crystals cool" - PennStateExtension Freezing. 

We don't care about freezing though, what about cooling ourselves? 

"Water evaporating takes quite a lot of heat away -- 540 calories per gram -- when it evaporates. That’s enough to cool down 540 grams of water by a degree, or 50 grams of water a little more than ten degrees. If you are not very careful to replace the lost heat energy during the evaporation, the temperature will go down." - Physics Van (University of Illinois). 

What the university is trying to say is that as water evaporates it takes a very large amount of energy with it and cools its surroundings. This is why you feel cooler as you sweat or when you pour water onto yourself. Coincidentally it is also why cooling and evaporative towels/vests work so well. So when you feel a damp cloth or towel on your skin it feels cold. It's because it is literally absorbing the heat energy out of you to allow it to change phases.