There is a small, stubborn argument playing out on sills across cold-season homes. On one side you have insulation and builders and a hundred-dollar plastic film kit you never wanted to buy. On the other side you have a humble ceramic bowl with table salt and tap water, sweating away on a chilly windowsill. I am going to insist, for reasons I can show you and for reasons I also cannot fully measure at your window, that the bowl deserves credit. It will not fix everything. But it answers a question most people get wrong when they blame their windows on insulation alone.
Why windows sweat in winter and why blaming insulation is lazy
Condensation on glass is not some moral failing of your house. It is physics. Warm moist air meets a cold surface, the air cools, the moisture condenses. That is it. People point fingers at insulation because when the room is colder more condensation shows up, and insulation does change the temperature of surfaces. But the real villain in nearly every room with recurring morning drips is humidity inside the living space. You can perfectly insulate a house and still get steamed-up glass if you live with kettles and long showers and a drying rack full of shirts.
An imperfect observation from my own apartment
I used to wipe my bedroom windows every morning. The ritual bored me into resentment. I am not proud of the tiny passive-aggressive things we do to domestic life to feel like we are in control. Then a friend who grew up in caravans laughed and said try the salt. I tried it because the alternative was to keep buying tiny battery dehumidifiers that always stopped working after a winter. The bowl did not feel very authoritative. It felt like a dare. Within a week the rivulets that wanted to run down the glass no longer formed. The edge fog stayed but the dripping stopped. I kept the heating low and opened the window sometimes and the bowl kept doing its quiet work.
The chemistry in plain language
Table salt is hygroscopic when conditions push it to be. That means under sufficiently humid indoor air salt will attract water molecules and form a brine. The bowl acts as a tiny moisture sink. It does not teleport humidity out of the house. It simply creates a close by low barrier to where water vapour prefers to end up. Think of it as a local agreement between the sill and the air not to flood the glass. In practice this matters a lot at the scale of a single window since condensation is often a microclimate problem around one cold pane or a sill over an unheated wall.
Limits you should accept
Salt stops working when it is saturated, when ambient humidity is too high, or when airflow is so poor that moisture just piles up everywhere. If you live in a flat where drying clothes indoors is normal, or you keep showers steamy without ventilation, a bowl may help a little but it will not fix the root cause. The sensible plan is to treat the bowl as a targeted stopgap and not a permanent replacement for adequate ventilation. I write that as someone who values thrift and hates waste. There is dignity in temporary tactics.
What experts actually say
You can limit window condensation by warming the window surface by adding storm windows another pane of glass or by covering windows with plastic.
Hellevang is talking about the broader toolkit and the piece I keep returning to is warming the surface and lowering indoor humidity. The bowl of salt water sits in the narrow gap between those two strategies. It is not a substitute for better glazing or added ventilation but it is a pragmatic immediate fix, affordable and low tech.
Why people online swear by it and why some scientists shrug
The net is full of confident voices who have seen their windows stop weeping after a ceramic vessel was introduced. That anecdotal evidence is real and consistent enough to merit attention. Countering this are measured lab-style takeaways: salt only becomes very effective above certain relative humidity thresholds. In many modern homes indoor humidity in winter lives below that threshold for much of the day. The bowl will therefore often be most effective in rooms where humidity spikes at night such as bedrooms with breath moisture or bathrooms without extractors.
My interpretation
The online chorus and the laboratory caution are not contradictory. They simply describe different conditions. Salt is a modest actor with a narrow but useful role. In many rooms it works like a small local dehumidifier. In some rooms it does little. You cannot treat it as universal medicine. But you should not dismiss it either because it asks so little and gives so much when conditions fit.
How to use the bowl so it actually helps
Place a shallow bowl on the coldest part of the sill. Use table salt because grain size matters. Add a little water to create a thin brine. Replace the salt when it clumps into a wet crust. The point is not to make the prettiest vignette for social media. The point is to maintain a local sink that intercepts moisture before it meets cold glass. Some people prefer silica sachets or store-bought moisture absorbers. Salt performs comparably in brief experiments and costs less. It is not glamorous but it is honest.
The moral of the small bowl
There is an intellectual error that people make when faced with condensation. They zoom out too quickly and aim big. Insulation is expensive and structural. Salt is tiny and cheap. The house is not an either or. Fixes that are cheap and local deserve their moment. They also teach humility: many domestic problems can be handled by attention rather than renovation.
Summary table
| Problem | What the bowl does | When it helps | When it does not |
|---|---|---|---|
| Morning dripping on window panes | Creates a hygroscopic local sink that absorbs some indoor moisture | Rooms with intermittent humidity spikes low to moderate overall humidity | Very high humidity homes or systemic ventilation failures |
| Widespread damp and mould | Minor local relief only | As a short term mitigation while you fix ventilation | Not a solution for structural leaks or chronic ventilation problems |
| Blaming insulation | Clarifies that humidity is usually primary cause | When condensation appears on otherwise cold single panes | When windows are poorly sealed or frames are failing |
FAQ
Does a bowl of salt water actually remove moisture from the air
Yes but only locally. Salt pulls water into solution when relative humidity is high enough or when the salt surface encounters moist air often. The bowl creates a micro zone where vapour prefers to condense into brine. It does not ventilate your whole house. Use it as a local, temporary mitigation not an all house cure.
How often should the salt be replaced or refreshed
That depends on room conditions. If the salt clumps into a moist crust replace it. In a modestly humid bedroom that might be every few days. In a drier living room every couple of weeks. If you find yourself changing it daily you likely have a larger humidity source that should be addressed by ventilation or behavior changes.
Can salt damage window frames or paint
Direct contact with wet brine can be corrosive to metal and may stain or warp certain finishes. Use a ceramic or plastic bowl and set it on a small saucer to catch spills. Keep the bowl slightly away from timber trim and never pour brine into paintwork or joinery deliberately.
Is the bowl a replacement for a dehumidifier or better windows
No. The bowl is a local, inexpensive stopgap. A dehumidifier actively moves moisture out of the air and is appropriate for chronically damp homes. Upgrading glazing and improving insulation changes surface temperatures and reduces condensation potential. Use the bowl while you plan larger changes or when your budget simply cannot stretch to a mechanical fix.
Why do some people find it works when others say it does not
Place and timing. Condensation is local and temporal. A bowl helps where humidity spikes against a cold pane. It will do nothing where humidity is uniformly high or where the pane is already well above the dew point. People test the trick under different conditions and reach different conclusions. That variability is not an argument against the method; it is an argument for understanding context.
Try it if you want to stop the morning mop. Keep expectations modest. If, after a reasonable trial, the bowl is not helping, then escalate. But if you find the bowl keeps your sill dry and your mornings quieter then you have reclaimed a tiny corner of domestic sanity without paying for a gadget or an installation. That feels worth a bowl of salt to me.
