Misinformation has struck again! For a while now, clickbait sites have been churning out catchy “articles” most likely written by interns who slept through physics class and bottom-of-the-barrel AIs. And the worst part of the story is that so-called serious mainstream media outlets are parroting this scam without even a shred of fact-checking!

The miracle hack of the moment? Place a bowl of salt water on your windowsill to “dehumidify your home” and “lower your heating bill”. Just like that! A bowl of salt water… to cut your heating bill 😀 We’d have had a good laugh if millions of readers weren’t currently placing bowls of brine on their windowsills believing it’s an established scientific fact. It has to be said that this bit of fake news is most often spread using the most classic clickbait playbook: What! You don’t know about this so you’re a loser? Do it right now! Impress your friends with this awesome hack! Save hundreds of dollars a year with this one simple trick… And we could keep this list going for ages because this nonsense has been recycled on an industrial scale. So let’s set the record straight. Because here we deal in rigor, not in copy-pasting garbage.

The clickbait argument is that salt is hygroscopic

The central argument across all these posts revolves around the fancy word “hygroscopic”. It means exactly this: something that absorbs moisture from the air. Salt is hygroscopic. That is absolutely true. Because NaCl (sodium chloride), in other words your good old table salt, is indeed an ionic compound whose sodium (Na⁺) and chloride (Cl⁻) ions exert a strong attraction on polar water molecules. This is basic high school chemistry. So far, no problem whatsoever.

But things go completely off the rails when these modern-day snake oil merchants tell you to put this salt… in water?! And that’s where the whole thing falls apart. Because salt dissolved in water is called brine. And brine is not a moisture absorber. It’s actually the exact opposite.

The physical principle that nobody bothered to check

Hold on tight, we’re about to do a bit of thermodynamics. But don’t worry, we’ll keep it simple 😉 Every saturated salt solution has what’s called an equilibrium relative humidity. That’s the relative humidity this solution will naturally try to maintain in an enclosed space. This isn’t some crackpot theory, it’s a measured and documented fact established by the American National Bureau of Standards (now known as NIST) and confirmed by 21 independent studies totaling over 1,100 individual measurements. And the verdict is crystal clear: a saturated NaCl solution stabilizes relative humidity at around 75%. Read that sentence again and burn that 75% figure into your brain.

The bowl of salt water doesn’t dehumidify… It humidifies!

Now ask yourself this: What’s the relative humidity in your heated living room during winter? Answer: Between 35% and 60% in the vast majority of homes. Sometimes even lower if you crank up the heating. And that’s exactly the problem! Your bowl of brine is programmed by the laws of physics to reach equilibrium at 75%. But your living room sits at 50%. So what’s the bowl going to do? It’s going to release water vapor into the air to try and push ambient humidity back up toward its equilibrium point. Yes, you read that right: Your so-called “miracle dehumidifier” is actually a humidifier. Which is basically like turning on a heater to cool down your house.

For your bowl to actually absorb moisture, the ambient air would need to exceed 75% relative humidity. That does sometimes happen very locally, within a few centimeters of a freezing cold window where a microclimate forms. But we’re talking about a few milliliters captured within a radius of a few centimeters. That’s like trying to drain a swimming pool with a teaspoon.

But what about dry salt for dehumidifying, then?

Hold on! Let’s not throw the baby out with the (salty) bathwater. Dry salt genuinely does work as a moisture absorber. Coarse salt placed in an open container will indeed attract water vapor from the air, gradually soak up humidity, and eventually liquefy into brine. This is the principle of deliquescence and it’s an indisputable physical fact.

Except here’s the catch: Even dry salt has its limits! A couple pounds of salt will absorb at most about a pint of water before it’s completely saturated. To put that in perspective, a decent electric dehumidifier extracts that much in a few hours. Your pile of salt takes weeks to get there. And once it’s saturated, you have to replace it.

The only marginally useful application would be using dry salt in a closet, a chest, a poorly ventilated dressing room… Basically, in enclosed spaces with a very small volume. But definitely not in a 200 sq ft room where you’re drying your laundry. And above all, commercial moisture absorbers don’t use table salt but calcium chloride (CaCl₂), a far more powerful industrial salt that can absorb up to 6 water molecules per molecule of salt. It’s in a completely different league from the NaCl in your salt shaker.

The real solutions for window condensation

Let’s get back to the original problem: condensation on your windows. Condensation forms when the warm, humid air in your room hits the cold surface of the glass. Water vapor turns to liquid and droplets appear. And eventually, unfortunately, mold moves in. It’s a real problem that affects millions of households. But the solution is not a bowl of brine. There are, however, methods that actually work. Methods that have been known and documented for a long time.

Air out your home for 5 to 10 minutes a day. Yes, even in winter! By opening your windows wide for a few minutes, you replace the humid indoor air with cold outdoor air that, once warmed up, will be much drier. It’s counterintuitive but it’s physics because cold air contains less water in absolute terms than warm air. It’s the most effective method, the simplest, and it’s completely free.

Control your moisture sources. Don’t dry your laundry in living areas. Use a range hood when cooking. Close the bathroom door during and after your shower. Check that your mechanical ventilation system is working properly (a tissue held up to the extraction vent is all it takes to test it).

Improve your window insulation. Double glazing, seals in good condition, shutters closed at night… Basically, anything that reduces the temperature gap between indoor air and the glass surface mechanically reduces condensation. It’s just common thermal sense.

Use a hygrometer. A small device costing a few bucks that gives you the actual relative humidity in your room. Aim for between 40% and 60%. If you’re regularly exceeding 65%, you’ve got a problem that needs serious attention, and no bowl of anything is going to make a lick of difference.

The real issue is thermal bridging

If you’ve got chronic condensation in the same spot, it’s not a humidity problem. It’s a thermal bridge problem. And no bowl, no chemical absorber, and no electric dehumidifier is going to fix that.

A thermal bridge is an area of your building where insulation is broken or insufficient. It could be a concrete lintel running through the wall without insulation, a poorly installed window frame, a corner between two exterior walls, a balcony slab that creates a direct link between inside and outside… At that spot, the interior wall surface is much colder than the rest. And when the warm, humid air in your room touches that cold surface, water vapor inevitably condenses. It’s just physics, not bad luck.

The trap is that many people see condensation and think they have a humidity problem. So they buy a chemical absorber based on calcium chloride (those little plastic tubs with a refill cartridge you have to replace every 4 to 6 weeks for an annual cost that can exceed $200). Or worse, they invest in an electric dehumidifier that runs around the clock and drives up the electricity bill. All of that to treat the symptom while the cause remains untouched. It’s like popping painkillers every day for a toothache while refusing to go to the dentist. It eases the pain for a while and ends up costing way more than the actual fix.

The right approach is to identify and treat the thermal bridge. In practical terms, try to locate the cold spots in your home with a simple infrared thermometer (you can find them for under $20, it’s a tool everyone should own). To do this, measure the surface temperature of your walls, your window frames, and the corners. If you find a difference of more than 7 to 9 °F compared to the rest of the wall, you’ve found your thermal bridge.

The solutions depend on the type of thermal bridge. A poorly insulated window frame can often be fixed with caulking and insulating tape for just a few dollars. An exposed concrete lintel, on the other hand, will require an insulating casing or a thermal bridge corrector. A cold wall corner can be improved with a thin insulation panel installed on the interior side. For more serious cases (balcony slabs, below-grade walls), you’re getting into major renovation territory.

The key takeaway is that fixing a thermal bridge is a one-time investment that solves the problem for good. And as a bonus, you genuinely reduce heat loss, which means your heating bill actually goes down for real. Not by zero like with some hypothetical bowl of brine, but in the range of 5 to 15% on your heating costs for a home with several untreated thermal bridges. Now that’s a real low-tech solution, sustainable and cost-effective in the long run. Sure, it’s less Instagram-worthy than a beautifully photographed bowl of salt, but it’s infinitely more effective.

The real scandal is the misinformation pipeline

What’s fascinating (or rather depressing) about this whole story is the mechanics of how it spreads. Some initial article gets pumped out, probably by an AI or a rushed writer who’s never cracked open a physics textbook. The headline is catchy and the keywords are well placed. So Google rockets it to the top of the results. No surprise there, since it doesn’t rock the boat. A second site picks it up with some light paraphrasing. Then a third. Then a mainstream outlet that calls itself serious publishes it in turn, adding bullet points and a pretty photo of a bowl on a windowsill.

And that’s how a physical absurdity becomes a home tip validated by experts. It’ll be read and taken as gospel by hundreds of thousands of people. And nobody in the chain took five minutes to check if any of it was actually true. Nobody typed “NaCl saturated solution equilibrium relative humidity” into a search engine. Apparently the word “hygroscopic” was enough to give the whole thing a scientific veneer.

It’s the exact same mechanism as political or health misinformation: Virality rewards the sensational, not the accurate. And in the field of ecology and “green hacks”, this phenomenon is particularly insidious because it discredits the low-tech solutions that actually work.

Who spreads this kind of misinformation? A world tour of gullibility

This fake hack has been published and republished without any fact-checking by a staggering number of media outlets, including titles that claim to be serious. Here’s a sample that’s far from exhaustive, because otherwise we’d still be here tomorrow:

On the US and Canadian side, House Digest and The Weather Network took the bait. In Germany, the IPPEN.MEDIA regional networks (Ludwigshafen24, Mannheim24) piled on by inventing a “Finnish trick” to make it all sound more exotic. In Spain, it was none other than ¡Hola! (the celebrity magazine), El Economista (a business newspaper, no less!), Infobae and La Nación that spread the nonsense.

In France, Presse-citron (which belongs to the same group as 01net and Journal du Geek) had the nerve to publish no fewer than three different articles on the same recycled topic. Yahoo Actualités France picked it up without batting an eye. 20 Minutes, Elle Adore, Demotivateur, Comment économiser, La Provence, Maison et Travaux, and plenty of others all jumped on the bandwagon.

In the UK, the Daily Mirror seems to have kicked the whole thing off by quoting a certain Andy Ellis, a “home and garden expert” at Posh.co.uk which is a décor website. One single guy spouting nonsense on a décor site… and suddenly it’s gospel truth for the entire planet. The Daily Express, Irish Mirror, HuffPost UK and Homes & Gardens followed without question.

After all that, here’s a question: If these “newsrooms” are capable of publishing advice that contradicts basic thermodynamics without taking five minutes to verify it, how much credibility should you give to the rest of what they publish? It would have been dead simple to do a quick source check to avoid publishing complete and utter BS. Personally, it took me less than 5 minutes to verify on DuckDuckGo. Well, it wasn’t even really a verification because I smelled the scam a mile away. And that’s how it’s done when you’re a serious media outlet like NovaFuture: You do your homework before writing nonsense.

Here’s an example of what serious work is based on: L. Greenspan, “Humidity Fixed Points of Binary Saturated Aqueous Solutions”, Journal of Research of the National Bureau of Standards, 1977, 81A(1), pp. 89-96. Data confirmed by NIST (National Institute of Standards and Technology), etc.

Conclusion: What you should take away from all this

But it’s not just mainstream media and clickbait sites that deserve the blame in this story. If they behave this way it’s because they know their audience all too well. People hungry for sensationalism who’ll share this stuff into the void of Facebook and the like just to look smart. Trying to grab their pathetic few seconds in the spotlight with a well-oiled routine that goes something like: “Check it out, I’m smart because I know about this trick and you don’t.” And among those who didn’t know about the oh-so-amazing super hack, plenty will want to shine just as bright as a firefly at noon by reposting it themselves. And that’s how you create nothingness out of nothing.

Welcome to the era where commercial media have virtually no counterweight left to prevent this kind of unacceptable drift. A world where a self-proclaimed home and garden expert on a British décor website becomes the go-to scientific reference for dozens of newsrooms around the globe. A world where a single scientific word like “hygroscopic” is enough to turn a thermodynamic absurdity into a clever tip you share between two grandma’s recipes.

But you’re all good! You’re on NovaFuture 🙂 Which means you won’t be caught looking ridiculous with your bowl of coarse salt sitting on your windowsill 🙂 And hey, if you’d like to dodge other embarrassing moments, please take a few seconds to buy us a coffee. It’ll keep us motivated to unearth more of the rubbish that commercial media churn out so well. And above all, a huge thank you in advance for taking a few extra seconds to share this article with the people around you, because unlike mainstream media and clickbait sites, we get zero favors when it comes to search rankings. In other words, without at least some support from our readers, we’re condemned to remain a free media outlet with limited reach. So to take things up a notch, let’s revive the golden age of “Don’t hate the media, become the media!” Because your power to create and share truly matters. And when it comes down to it, we all have a part to play if we want to build a better world. Thanks for reading and see you very soon for new adventures.