The formula of the perfect bath

Telegraph

18-05-2025

Last night at around 7pm I turned the taps on, poured in a careful dribble of my favourite, wildly expensive Olverum bath oil (recently granted a royal warrant by the King, no less) and ran myself the hottest bath I could bear into which I sank, tingling slightly as my skin hit the water, to enjoy a good half an hour of luxurious soaking.
My formula differs slightly from what emerges as the 'perfect' way to enjoy a bath: apparently at 8pm on a Sunday evening with the water temperature at 39.8c, for 22 minutes. Now, this is according to the results of surveys by British Gas and Victorian Plumbing, so perhaps we can take it with a pinch of (bath) salts. But it emerges that there are, indeed, ways to optimise your bathing ritual. I spoke to the experts to find out where – and if – I've been going wrong.
Temperature
Nearly a quarter of the 2,000 adults surveyed by British Gas said that, like me, they prefer the water to be as hot as they can bear – usually between 43C and 45C. This, however, is really too hot, says Penny Hamilton, head of product at Westlab, which makes bath salts. 'If you're someone who's got dry, sensitive or itchy skin, you should keep the water temperature at about 36/37 degrees,' she says.
For muscle relaxation, or for those who want to use their bath as a way to relax before bed, the optimum temperature is between 38C and 40C, says Hamilton. 'If necessary, heat the room up before you have a bath because you don't want to put your body under unnecessary stress if there's an excessive temperature difference when you get out,' suggests Suzanne Duckett, author of Bathe: The Art of Finding Rest, Relaxation and Rejuvenation in a Busy World – although she also confesses to doing a lot of hot bath, cold shower-alternating, 'especially on a Saturday morning to reinvigorate for the weekend – it's a real livener.'
Interestingly, there is a reason why I like my bath hotter than hell, and my husband yelps if he so much as sticks a toe in: because women typically have a higher core temperature but lower extremities temperature, as well as a lower metabolic rate than men, meaning they produce less heat and feel colder at the same temperature. Doesn't mean a boiling bath is necessarily good for us, but does explain why the water's never hot enough for your wife.
Timing
If you're using your bath as a way to prepare for bed, the best time to hop in is one to two hours before bedtime. That's according to a 2019 study from the University of Texas, which concluded that bathing at this point aids the natural circadian process, and increases the chances of not only falling asleep quickly, but also of experiencing better quality sleep.
A 2023 Japanese study that tested the efficacy of showering, short bathing and long bathing on sleep also found that a long bath of about 20 minutes in the evening, at 40 degrees, raising both skin and core temperature, came out top. This is because, if you increase your core temperature via a hot bath, there will be a greater subsequent temperature drop before you go to sleep, which signals to your body it's time to start producing the sleep hormone melatonin, helping you nod off more easily.
Depth
Personally, I think there's no point in having a measly bath with water that only laps at your sides – you're better off having a shower. The majority of scientific studies on bathing run the water to thorax (chest) level – but again, it depends on the purpose of your soak. If you're a cold woman who wants to warm up, like me, submerge yourself and your extremities. If you're a wussy man who can't stand the heat, something shallower and more lappy might suffice.
Length of time
The Japanese might consider 20 minutes a long soak, but for hardened bathing professionals like me, that's a mere splash in the tub. Victorian Plumbing's research found that for optimum relaxation, 21 minutes is the sweet spot (the same study found people were most relaxed post-bath if they spent that 21 minutes scrolling on their phones), and that you're likely to start getting dehydrated at around 28 minutes.
Extending your bath to 27 minutes can lead to the ultimate sleep-inducing experience, but only if you spend it reading a book. A 2018 study found that a 30-minute bath can significantly reduce stress from conditions like PTSD and anxiety. If you suffer from eczema, the National Eczema Association recommends restricting your bath to 10-15 minutes. In short, bathe for however long you like.
Frequency
British Gas's survey found that Brits take an average of 96 baths a year – the equivalent of two a week. It also found that one in 10 people admitted to having THREE baths a day. This, says Professor Carsten Flohr, a consultant dermatologist at St John's Institute of Dermatology in London, is too much.
'Higher frequency of bathing can disrupt the skin barrier because water dries out skin,' he explains. Studies differ as to how often is too often, especially if you suffer from skin conditions such as eczema, although Prof Flohr says it's fine to bathe daily with eczema as long as you use the right product to wash with (of which more later) and apply lots of moisture to your skin afterwards.
Sharing water / position in the queue
At boarding school in the early Nineties, we had no showers, only baths, and also bath rotas. We weren't allowed one every night, and when we were rota'd for one, we had to share. Consequently, baths have remained something of a congenial activity for me. Similarly, I know a couple who have been married for many happy years and attribute much of that happiness to conjugal bathing.
'In Japan and South Korea they value what they call 'skinship', used to describe non-sexual touching and an intimacy between family or friends,' says Duckett. 'Co-bathing is widely considered the ultimate scenario in skinship, because bathing naked symbolises the removal of social trappings and barriers that separate us. Hierarchy and status are not apparent or important when naked.'
These days my bathtub is too small and my children/husband too large to comfortably share, (plus I'm increasingly keen to maintain family hierarchy as my children become teenagers) although I'm not averse to passing my water on to someone else or even, in extremis, taking theirs. And although more eco-friendly, opinions on this vary. 'Absolutely not,' states my best friend.
Type of bath and tap placement
Rolltop baths look impressive, but alas, for traditionalists, they don't always make the best tub of choice. 'Metal baths get really cold very quickly,' points out interior designer Nicole Salvesen, who suggests a modern, mineral composite alternative (which will also resist cracking and chipping) is better. 'You want them to look very traditional in style,' she says firmly; 'and taps need to be along the side [for ease of turning on or off].
Definitely don't get a plastic bath, because it will feel as if you're sitting in something very thin and uncomfortable.' The optimal tub length is around 1800cm, says Salvesen, unless you're an actual giant. You also want to consider soaking depth, which is the vertical distance from the bottom of the tub to the highest water level, and determines how much of your body will be submerged when you're bathing – ideally you want it to cover most of you, including your shoulders.
If you're over six feet tall, a soaking depth of around 15 inches is ideal; shorter people might prefer a shallower tub. If you're buying a new tub, the best thing to do is climb into the thing to test it out – as well as how easy it is to get in and out.
As for placement, put it wherever you like – although consider plumbing. If your loo is in the same bathroom it's likely to be close to the bath because again, plumbing, although it's recommended to maintain a minimum clear space of at least 700mm between the front edge of a fixture and any opposite fixture. Personally, I like my bath to butt up against the wall; a gap behind my head makes me feel mildly unsafe.
Unguents
In the UK, what you put in your bath is nearly as important as putting yourself in it, largely because, as Hamilton points out, 'our water isn't great. The main reason why we started as a company was because our kids had eczema, and adding salts to their baths made a massive difference to softening the water. I would never get in a bath without salts or oils in it, otherwise you're just sitting in chlorinated water, which can be very drying to the skin.'
'Epsom salts are an excellent source of magnesium, dubbed as the miracle mineral to aid sleep and calm the nervous system – the Romans added it to their bathwater,' says Duckett, who buys 25kg sacks online. A good idea as, says Hamilton, a mere handful is pointless; 'we'd recommend a minimum of 250g in a bath for salts infused with essential oils, and 500g for magnesium flakes or Epsom salts on their own.'
Essential oils in the bath can help you relax; lavender is used in many sleep blends. 'Opt for French, high-altitude lavender oil, because it contains higher natural linalyl acetate (ester) levels, so the slumber factor is enhanced,' advises Duckett, who adds that you should add the oil to an already-run bath, as adding oils, which are very volatile, to running water means that they'll just disappear up into the steam.
She has developed her own bath ingredient, called Onolla Down to Earth Mud, which includes magnesium, calcium, chromium and copper and has been certified 'curative' by doctors in Hungary. Just make sure you don't put any nasties in your bath: use a soap substitute if you've got sensitive skin, advises Prof Flohr, and avoid anything containing sodium lauryl sulfate, which may produce ginormous bubbles but will strip your skin.
Accessories
Here, the world is your oyster. Want to relax? Turn the lights down (or off) and light some candles. Music? According to psychologist Dr David Lewis-Hodgson, who specialises in stress, relaxing songs have narrow note sequences that go from high to low, are around 90 beats per minute and have a 4/4 beat – helpfully, he has created a Most Relaxing Songs Ever playlist on Spotify (although avoid it if you can't stand Coldplay).
Forget scrolling the news, unless you're happy to take your phone into the bath; if you're worried about dropping your book in the water, try an audiobook or podcast, or the newest generations of Kindle are waterproof.
Ensure you have a fluffy towel warming somewhere nearby for a comfortable exit: look for grams per square metre, or gsm, on the label (the higher the number, the heavier the towel); Egyptian and Supima cottons have long fibres and are more absorbent.