The Science Behind Why You Can’t Decide If Your Laundry Is Wet Or Just Cold

Dr Karl helps us answer one of winter's foulest riddles.

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Today is the first week of winter, which means we’ll soon be playing everyone’s least favourite game: Is my washing hanging on the line still wet or simply cold?

There can be no doubt that drying your clothes on a conventional washing line at this time of year takes an excruciatingly long amount of time. Worst of all, even if you manage to dodge torrential rainfall (thanks La Niña) and catch some sunlight, you’re often greeted with laundry items that still feel impossibly wet.

“How can they still be wet? They’ve been on the line for three days!” you mutter, but regardless you’re stuck with laundry that is stuck in a netherworld between cold and damp, like the linen equivalent of Schrodinger’s cat.

So are your poor clothes actually getting wet somehow? Or is this all some kind of scientific illusion? To settle the score once and for all, Junkee spoke to acclaimed scientist and professionally know-it-all Dr Karl Kruszelnicki.

Dr Karl told Junkee that by hanging our wet washing on a clothesline, we’re relying on the process of evaporation to remove the water molecules and thus render our clothes dry. As water molecules escape into the atmosphere from our wet clothing through evaporation, they also lower the temperature of the local area, which is usually unnoticeable on a hot and sunny day.

Obviously, in winter this local average temperature is a lot colder. Dr Karl says that the reason we have such difficulty telling wet apart from cold in colder months has to do with the touch receptors in the human body.

“If you’re touching something that is cold, you have temperature sensors in your hand. You have sensors in your fingers for hot, cold, dull touch and sharp touch as well as vibrations,” Dr Karl told Junkee. n“You don’t have a direct sensor for wet, what you have is a sensor for heat. If something is wet, it’s more likely to evaporate and then remove some heat from the local area. So if you touch something that’s cold, you think ‘that’s cold’.” 

“But if you touch something that’s wet, there’s that link in your mind where you get a little bit confused. Like you’re taking off the sheets at the end of the day and they’re cold, but are they dry? It’s because you don’t have a sensor for wet.

“So that’s why you get that confusion. And you’re thinking, ‘I know they’ve gotta be dry because they’ve been out in the sun all day’ but what I’m feeling is cold, and normally when I feel something that’s cold it’s associated with water, water evaporating.”

Dr Karl goes even further to say that even without the usual sunshine and high temperatures of summer, the wind will also effectively make your wet washing dry. “In Europe, they put clothes out on a cold dry day, and even though it’s cold and there’s no sunshine the wind will carry away the water molecules,” Dr Karl told Junkee.

So this winter, you can relax if your clothes still seem impossible wet after a lengthy time on the washing line. They’re probably just cold.