The first time I saw a bowl of salt water sitting quietly on a winter windowsill, I thought my neighbor had forgotten to put away something from the kitchen. Outside, the sky was that flat, heavy gray that makes the whole street look like it’s under a wet blanket. Inside, her double-glazed window was clear. No mist. No heavy droplets running down like tears. Just a calm pane of glass and a small, white bowl, half filled with water and chunky salt crystals.
She laughed when I asked what it was. “My winter aluminum foil,” she said. And then she told me this tiny habit had changed the way her apartment felt on damp, cold days.
A simple bowl. A handful of salt. And suddenly, the window wasn’t the cold enemy anymore.
Windows that sweat, rooms that chill
On winter mornings, plenty of homes have the same scene: beads of water clinging to the glass, slowly forming thick drops that slide down and pool on the sill. The window looks like it’s crying. The air near the glass feels colder, heavier, as if the outdoors is sneaking in. You wipe the condensation with a sleeve, a cloth, a paper towel. Ten minutes later, it’s back.
This “sweat” on the window is more than an aesthetic problem. It leaves black stains in the corners, swells wooden frames, rusts metal. You open the window to dry it, then shiver as the precious heat escapes.
A friend living on the ground floor of an old building told me she had to mop her windowsills every single morning. Her radiators were blazing. Her electric bill too. Yet the glass was constantly fogged, as if she was running a sauna. She tried everything: running the extractor fan more, wiping with vinegar, blasting the heat for an hour before going to bed.
One day, after reading about it online, she placed a deep bowl of water with coarse salt near each window. It looked more like a cooking prep station than a humidity fix. A few days later, she noticed she didn’t need to grab a towel as often. The glass was still cool, but not dripping. The puddles on the sill had simply… stopped forming.
What happens is simple physics dressed in everyday clothes. Warm air in a heated room holds moisture from showers, cooking, breathing, even drying laundry. That warm, humid air hits the cold glass. The temperature drops. Water can’t stay suspended, so it condenses on the surface. Think of your window as a giant cold drink in summer, constantly attracting moisture.
Salt acts a bit like a silent sponge. It’s hygroscopic, which means it “pulls” water from the air and traps it. The bowl of salt water becomes a little humidity magnet right where the problem starts: at the window. The less water in the air nearby, the less condensation clings to the glass.
The winter “foil” trick: how the bowl really works
In summer, people tape aluminum foil to windows to reflect heat and keep rooms cooler. It’s not pretty, but it’s effective. In winter, think of the bowl of salt water as the invisible version of that: no shiny glare, no DIY craft project on your glass, just a discreet tool fighting against humidity and heat loss.
To try it, take a small to medium ceramic or glass bowl and fill it halfway with water. Add a generous layer of coarse salt or rock salt. Stir lightly. Then place it directly on the windowsill or on a small tray just in front of the pane, as close as you can get without risking spills.
A lot of people stop at one bowl for the whole apartment. Then they complain it “doesn’t work”. Let’s be honest: nobody really does this every single day with scientific precision. Yet it helps to treat each window, or at least the ones that fog the most. For a bedroom with one large window, one decent bowl is fine. In a living room with a bay window or several panes, two or three small bowls spread along the sill work better.
Change the salt when it looks soaked, crusty, or when a salty film appears on the surface. That’s usually every week or two, depending on how damp your place is. And yes, it feels a bit like tending to a plant: small, regular care, not a one-shot miracle.
“You’d be surprised how much water a simple bowl can ‘drink’ in a week,” says a building caretaker in a damp seaside town. “I tell my tenants: try it for one month. You’ll see the difference on the glass and even on the smell of the room.”
To give this simple habit a bit of structure, think in terms of small steps:
- Choose stable, heavy bowls so they don’t tip over near curtains or plants.
- Use coarse salt rather than fine table salt, it lasts longer and absorbs more gradually.
- Place bowls where the air circulates slightly, not hidden behind thick curtains.
- Combine the bowls with short, sharp airing: 5–10 minutes of wide-open windows once or twice a day.
- Keep an eye on walls and frames: less condensation also means less mold colonizing the corners.
More than a trick: a different way to inhabit winter
There’s something almost old-fashioned about placing a bowl of salt water by the window. It feels like a grandmother’s answer to a modern energy problem. No connected sensor, no app, no buzzing device. Just a physical gesture that slightly changes the relationship between your home and the season pressing against the glass.
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*The truth is, we don’t control the weather outside, but we can play with the invisible climate inside.* Less condensation doesn’t just save the window frames. It makes the room feel drier, easier to heat, less heavy. Suddenly that corner by the window is a place where you can read or drink coffee, not a damp draft zone you avoid.
| Key point | Detail | Value for the reader |
|---|---|---|
| Salt absorbs humidity | Coarse salt in a bowl attracts moisture from the air near the cold glass | Reduces condensation and limits mold around windows |
| Strategic placement | Bowls need to be close to problem windows and refreshed regularly | Improves daily comfort with a nearly free, low-effort routine |
| Winter “foil” alternative | Like aluminum foil in summer, the bowl manages the exchange between indoor air and outdoor climate | Helps keep rooms more stable in temperature and less “wet” without ugly visual clutter |
FAQ:
- Does a bowl of salt water really work against condensation?
Yes, especially in small to medium rooms with moderate humidity. Salt is hygroscopic, so it gradually absorbs moisture from the air near the window, which leads to less water forming on the glass.- What type of salt should I use?
Use coarse salt, rock salt, or sea salt. Fine table salt works too, but it saturates faster and often clumps into a hard block, so you’ll need to change it more often.- How often should I change the water and salt?
On average every 1–2 weeks. If the salt looks mushy, forms a crust, or the bowl is almost full of cloudy water, it’s time to empty, rinse, and refill with fresh water and salt.- Is this enough if my home is very damp?
If you have serious humidity issues, this trick alone won’t solve everything. It’s a helpful complement, but you may need better ventilation, a dehumidifier, or to check for leaks and insulation problems.- Can I leave the bowls all winter?
Yes. Just keep them out of reach of small children and pets, refresh them regularly, and move them slightly if you’re cleaning or opening the windows wide. It’s a simple, long-term winter habit, not a one-off hack.
