The short answer: will a bowl of salt stop condensation? No, not on its own. Salt does absorb moisture from the air, but table salt only starts doing it in earnest once indoor humidity passes about 75 percent, and a single bowl can hold no more than about a third of a litre of water even in perfect conditions. A typical UK household produces up to 100 litres of moisture a week, according to the Energy Saving Trust, so one bowl on a windowsill is a small local helper, not a cure. It can take the edge off a steamed window overnight. It cannot fix the damp air that caused the condensation, and it is no substitute for ventilation.

Every autumn the same tip does the rounds in the UK press and on social media: put a bowl of salt on the windowsill and your windows will stay dry. It costs next to nothing, it needs no tools, and plenty of people swear it works. This article tests the claim against the chemistry, the numbers and the official guidance, so you can decide whether it is worth a place on your sill or just a place in the cupboard.

This is the folk-remedy companion to our two practical condensation guides. If your windows are already streaming, start with the fast-action routine, then come back here to judge whether salt deserves a role in the longer plan.

Why the bowl of salt hack keeps going viral

The tip resurfaces every autumn, and October 2026 was no exception. Brit Brief reported on 2 October 2026 that placing a bowl of salt on windowsills can keep windows dry in autumn and prevent condensation from developing, calling it a cheap alternative to a dehumidifier. Home improvement website The Spruce, quoted in the same report, put it carefully: “Placing a bowl of salt near the window can help to absorb moisture in the air before it can condense on the windows, though the amount of salt needed and the frequency with which you will have to replace the salt depends on the level of moisture inside the home.”

The idea is older than the current coverage. The Gazette Herald covered the same hack in November 2025, when bathroom and window specialists were recommending a bowl of salt on the sill as a natural dehumidifier for autumn and winter. Helen Godsiff, brand manager at Eurocell, told the paper that a bag of salt from any supermarket, usually for less than two pounds, placed in a bowl on the windowsill, can draw moisture from the air before it settles on the glass. Liam Spencer, owner of Northallerton Glass, explained that salt is hygroscopic, meaning it attracts and holds water, and that the salt needs replacing as soon as it turns hard or becomes damp itself.

First-person tests in the regional press sound convincing. A reporter for Edinburgh Live bought table salt for 65p from Sainsbury’s, filled a small bowl and put it on the windowsill before bed. The next morning there was very little condensation on the windows, and the salt bowl was moist to the touch. A Grimsby Telegraph reporter had a similar experience after ditching a 200 pound dehumidifier for a bowl of table salt costing under a pound: after several nights the usual pooling of water on the sill had stopped, and the salt had clumped together and gone slightly moist. Both accounts are anecdotes, not measurements, but they agree on the same detail: the salt visibly takes up water, and the window looks better in the morning.

The same coverage also carries a warning that often gets lost when the tip is shared. Andy Ellis at Vidalux told the Gazette Herald that the bowl is only a temporary solution, and that to tackle condensation properly you should focus on improving ventilation, opening windows regularly and using extractor fans, especially when drying clothes indoors. That warning is the honest version of the story, and the chemistry backs it up.

The science: salt only starts working at about 75 percent humidity

Salt absorbs moisture because it is hygroscopic. The ions in sodium chloride attract water molecules from the surrounding air. But the process has a threshold. Salt only begins to dissolve in the water it attracts, a process called deliquescence, once the relative humidity of the air around it passes a specific point known as the deliquescence relative humidity. For sodium chloride that point is about 75 percent relative humidity at room temperature.

The figure comes from peer-reviewed aerosol research. Wise and colleagues, writing in the Journal of Geophysical Research in 2007, measured single crystals of sodium chloride deliquescing at approximately 76 percent relative humidity at 291 Kelvin, about 18 degrees Celsius. A separate study of sodium chloride powder by Langlet and colleagues, published in the KONA Powder and Particle Journal in 2011, gives the deliquescence relative humidity as 75 percent at 25 degrees Celsius. The two numbers agree: below roughly three quarters humidity, a bowl of dry salt sits there doing almost nothing. Above it, the salt starts to pull water from the air, dissolve into brine, and keep pulling more.

That threshold explains both why the hack sometimes seems to work and why it so often disappoints. On a cold, wet November night in a bedroom with the door shut and two people breathing for eight hours, the air near the window can easily pass 75 percent humidity, and the bowl will start absorbing. On an ordinary evening with the heating on and the air drier, the same bowl will sit unchanged for days. Salt only begins to absorb water vapour at relatively high humidity, which is exactly when condensation is already at its worst. The bowl is working hardest in the conditions where the window is already losing.

The maths: what a bowl of salt can actually absorb

Even when the air is damp enough for salt to work, the capacity of one bowl is small, and the arithmetic is not on its side. At room temperature, about 36 grams of table salt dissolve in 100 millilitres of water, producing a saturated brine that is roughly 26 percent salt by weight. That solubility figure is standard chemistry, set out in the solution properties reference published by the Polytechnic University of Madrid.

Work it through for a bowl on a sill. A cereal bowl of table salt weighs roughly 100 to 150 grams. For all of that salt to dissolve into saturated brine, it would need to absorb roughly 280 to 420 millilitres of water from the air, about a third of a litre at most, and only if the air stays above 75 percent humidity long enough for every grain to dissolve. In practice a bowl left overnight absorbs far less than its theoretical maximum, which is why people report the salt going damp and clumping rather than turning into a puddle of brine. Clumping is the sign that the salt has taken up some water and is now spent.

Now set that against what a home produces. The Energy Saving Trust states that a typical household produces up to 100 litres of moisture a week from cooking, boiling kettles, showers and breathing. That is about 14 litres a day. A bowl of salt, at its absolute best, absorbs about a third of a litre before it needs replacing. That is roughly 2 to 3 percent of a single day of moisture, and only from the air immediately around one window. It is a thimble against a tap.

This is also why the hack looks better in a small room than in a large one, and better on one window than on a whole house. A bowl on a bedroom sill deals with the air in that corner of that room. It does nothing for the bathroom steam, the kitchen kettle or the laundry drying on the radiator two rooms away. Anyone selling it as a whole-house dehumidifier is selling a thimble as a bucket.

How to try it properly if you want to

If you still want to try it, the method is simple, and doing it properly costs nothing extra. Fill a wide, shallow bowl or small dish with table salt. Table salt is the better choice because its grains are finer, giving more surface area for the air to meet, which is why the Edinburgh Live test used it. Rock salt works too, and the Gazette Herald coverage quotes both, but the finer grains of table salt start absorbing sooner.

Place the bowl on the windowsill as close to the coldest glass as you can, since that is where the dampest air gathers. A wide bowl beats a deep jar because the exposed surface matters more than the depth. Give the salt a shake in the morning so it does not set into a solid cake, and replace it as soon as it clumps together or feels damp. Clumped salt has already absorbed what it can hold, and leaving it there does nothing. Fresh salt, dry from the packet, is the only kind that works.

Two cautions matter. First, keep the salt in the bowl. The Gazette Herald coverage warns that sprinkling salt directly onto a windowsill can damage wooden sills, corrode hardware and discolour uPVC frames, and brine is worse than dry salt for all three. If the bowl spills, wipe the brine up promptly. Second, treat the bowl as a supplement, not a solution. If you try it for a week and the windows are still streaming every morning, the bowl has told you something useful: the room has more moisture than a thimble can handle, and it is time for the measures below.

When a bowl of salt might actually help

The bowl is not useless, and it is worth naming the cases where it earns its place. A small, closed bedroom with one cold window and no extractor fan is the best case: the bowl sits in the dampest air in the room, the air passes 75 percent humidity overnight, and the salt takes enough water out of that corner to leave the glass clearer in the morning. A caravan, a boat cabin or a small box room fits the same pattern, because the volume of air is small and the bowl is close to the only cold surface.

It also works as a visible early warning. If the salt in the bowl clumps and goes damp every night, your room is spending hours above 75 percent humidity, and that is information worth having. The bowl is acting as a crude hygrometer, telling you the air is far wetter than it should be. The right response to that signal is ventilation and heating, not a bigger bowl.

What it cannot do is protect a whole house, dry out a damp wall, or replace a dehumidifier. The Energy Saving Trust recommends considering a dehumidifier for dealing with excessive moisture or for drying washing inside, and a plug-in dehumidifier removes litres of water a day, not millilitres. If you are choosing between a bowl of salt and a dehumidifier for a genuinely damp room, the dehumidifier is the answer every time.

What actually stops condensation

Condensation forms when warm, moist air meets a cold surface, and the only durable fix is to remove the moisture or warm the surface. The Energy Saving Trust guidance is the authority here, and its advice is straightforward. Keep trickle vents always open and clear of obstructions. Open windows several times throughout the day for at least five minutes, and longer if you can. Run extractor fans for at least 15 minutes after taking a shower or a bath, and run the cooker extractor whenever you cook, again for at least 15 minutes afterwards. Wipe windows and sills dry each morning, dry clothes outside where possible, and keep a steady background temperature in winter rather than letting rooms go cold.

One warning from the same guidance is easy to miss: do not fit new draught proofing in a room that does not have enough ventilation or where there is already a condensation problem. Sealing a damp room tighter traps the moisture inside and makes the condensation worse. Ventilation first, sealing second.

If your windows are already wet this morning, the fastest route to dry glass is the ten minute routine in our companion guide: wipe the glass and sill, open the trickle vents, open the window wide for five to ten minutes and run the extractor. For the whole heating season plan, the room by room prevention guide covers every room and every moisture source. Salt can sit alongside those measures on one sill. It cannot replace them.

When salt is the wrong answer

There are situations where a bowl of salt is not just inadequate but a distraction from a real problem. If condensation never clears during the day, if black mould keeps returning to the same corner, if wallpaper is peeling or plaster is crumbling, the cause is not a lack of salt. GOV.UK guidance on damp and mould states that damp and mould primarily affect the airways and lungs, that causes include building deficiencies, inadequate ventilation and condensation, and that removing surface mould will not prevent it reappearing. The cause has to be found and fixed, whether that is a leak, a failed damp-proof course, blocked guttering or a room that is never ventilated.

Mould is also a health matter, not just a cosmetic one. The Energy Saving Trust notes that mould can cause symptoms such as nasal stuffiness, wheezing, and eye or skin irritation, and that children, older people and people with skin or respiratory conditions are particularly at risk. A bowl of salt on the sill does not change any of that. If damp or mould keeps coming back, get the cause assessed by a professional, and if you rent, report it to your landlord in writing. Salt is a kitchen experiment. Damp is a housing problem.

Frequently asked questions

Will a bowl of salt stop condensation? Not on its own. Salt absorbs moisture only once indoor humidity passes about 75 percent, and a bowl of table salt can hold at most about a third of a litre of water. A household produces up to 100 litres of moisture a week, so one bowl can take the edge off a single window overnight but cannot stop condensation across a home. Ventilation, extractor fans and wiping the glass are what actually stop it.

Does rock salt work better than table salt? Table salt is the better choice for a windowsill bowl because its finer grains give more surface area, so it starts absorbing sooner. Rock salt works too and is often used in larger DIY dehumidifiers, but for a small bowl the finer grains of table salt are the practical pick. Either way, replace the salt as soon as it clumps or feels damp.

How much salt do I need for one window? A cereal bowl holding roughly 100 to 150 grams of table salt is the usual amount. At most that can absorb about 280 to 420 millilitres of water before it is fully dissolved into brine, and in practice it absorbs far less overnight. One bowl per window is the rule, since the salt only dries the air immediately around it.

How often should I replace the salt? Replace it as soon as it clumps together or feels damp to the touch, which in a damp bedroom can be every few days. Shake the bowl each morning to stop the salt setting into a cake. Salt that has already gone damp has absorbed what it can hold and does nothing until it is replaced with a fresh, dry batch.

Can salt damage my windowsill? Yes, if it escapes the bowl. Salt sprinkled directly onto a sill can damage wooden sills, corrode metal hardware and discolour uPVC frames, and salty brine is worse than dry salt. Always keep the salt in a bowl or dish, wipe up any spills promptly, and do not put a bowl of salt where it can be knocked over onto a wooden sill.

What works better than salt for condensation? Ventilation. Keep trickle vents open, open windows several times a day for at least five minutes, run extractor fans for at least 15 minutes after showers and cooking, wipe windows dry each morning and keep a steady background temperature. For heavy moisture, such as drying laundry indoors, a plug-in dehumidifier removes litres of water a day, while a bowl of salt manages millilitres.

Related reading

• How to get rid of window condensation fast: the 10 minute fix and the morning routine
• How to stop condensation on windows: the room by room guide for the whole heating season
• What temperature should you set your thermostat in winter?
• How to stop draughts in windows and doors without trapping moisture
• Should you bleed your radiators before winter?

Sources

• Energy Saving Trust: How to get rid of damp (a typical household produces up to 100 litres of moisture a week; trickle vents always open and clear; open windows several times a day for at least five minutes; extractor fans for at least 15 minutes after showers and cooking; wipe windows; dehumidifier for excessive moisture; do not fit new draught proofing in a room without enough ventilation; mould health symptoms)
• GOV.UK: Understanding and addressing the health risks of damp and mould in the home (damp and mould primarily affect the airways and lungs; causes include building deficiencies, inadequate ventilation and condensation; removing surface mould will not prevent it reappearing)
• Buckinghamshire Council: Keep your home free from damp and mould (wipe windows and sills every morning with a dry cloth; dry clothes outside where possible; keep heating steady in winter)
• Gazette Herald: UK households urged to use 65p hack to reduce condensation (Eurocell advice on placing a bowl of salt on the windowsill; salt described as hygroscopic and a natural desiccant; replace when hard or damp; Vidalux warning that it is only a short-term fix and ventilation is the real answer; warning that salt sprinkled on sills can damage wood, corrode hardware and discolour uPVC)
• Brit Brief: Salt, not dehumidifiers, keeps autumn windows condensation-free (October 2026 coverage of the salt hack; The Spruce quoted on placing a bowl of salt near the window and replacing it when it clumps)
• Wise et al., Journal of Geophysical Research, 2007: Hygroscopic behavior of NaCl-bearing natural aerosol particles (single crystals of sodium chloride deliquesce at approximately 76 percent relative humidity at 291 Kelvin)
• Polytechnic University of Madrid: Properties of some particular solutions (sodium chloride solubility 0.359 kilograms per litre of water at 15 degrees Celsius; saturated brine 26.4 percent salt by weight)