Is your kettle as loud as a drill?

There is nothing like Which? Conversation for learning about problems you do not realise you have. 🙁

To be serious, ordinary kettles are difficult for those with arthritis or weak wrists. Travel kettles are lighter but the quality of those I have seen is mediocre. It might be worth reviewing the better ones in the next Which? review of kettles.

We purchased the Prestige Eco 55845, a Which? best buy, because it only weighs at 0.6 kg. One reviewer complained that it was flimsy, but if flimsy means light weight then it’s excellent. It certainly boils fast and you can fill just one mug full, so it really is eco.

The downside is it is noisy. But then it is fast at boiling, so boiling just a mug of water means you don’t hear it for very long.

Quieter kettles tend to be much heavier. So you takes your choice!

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Boiling a saucepan of water on an electric hob is very quiet, so I assume that kettles are noisy because the base resonates much like the sound board on a musical instrument.

As you point out, David, some kettles don’t even pour properly, so I doubt that enough thought goes into their design. If you do get round to designing a quiet kettle, please could we have one with a PTFE coating so that limescale does not stick to it.

It’s little to do with the kettle resonating, but is to do with cavitation. Because the water is touching the element, the heavy current passing through the element causes it to get hot and pass that heat to adjacent water molecules. The electrons in the molecules get excited and expand, rising upwards. As they rise, they dissipate their heat rapidly to surrounding ‘cold’ molecules and collapse (cavitation). The cavitation makes the noise because it is a relatively violent reaction.

The kettle is much quieter once it is boiling because the quantity of cavitation falls off dramatically (all the molecules have become excited and equally hot).

With a hob (electric or gas), the element is not touching the water, so the molecules are far less excited and there is minimal cavitation. Hobs are far less efficient at boiling because there is a gap between the heat source and the water molecules.

In a modern electric kettle, the element is not in direct contact with the water in a kettle, but attached to the metal base of the kettle. This is normally a thin sheet of stainless steel. I reckon that a thicker aluminium base would be better, since it will not resonate. A PTFE coating would protect the aluminium from corrosion, but might not be sufficiently durable to be left with water in the kettle when not in use.

You are both right. The cavitation is caused by the water next to the hot surface reaching boiling point and becoming steam, expanding suddenly. What you need is as large a heating surface as possible, to dissipate as much of the hot water as fast as possible, maybe by having the heating base corrugated and yes why not coat it with a Teflon polymer although that is very hard to make stick to anything, so a better coating would be a fluorosilicone resin.

Fluorosilicone would be a good option, David, and a corrugated base would be stiffer and resonate less. Now we just need someone to make a prototype ‘Quietboil’ kettle. 🙂

I’d buy one. Our kettle gets tremendously excited and makes a phenomenal racket, drowning out all conversation during the last few minutes of the boil. This has got worse as the kettle has got older. It helps if we put one of those ribbed rubber mats underneath it to stop the transmission of vibration, but the screaming from the cold molecules as they get scolded by the hot ones is still alarming. Cavitation! I must remember that . . . should break the ice at parties.

A corrugated element base would certainly provide greater surface area but it would produce even more cavitation and be even louder, though it should improve efficiency.

Extra strength would irrelevant as vibration is insignificant.

Why is my pan of water on the electric hob so quiet?

Sorry – I see you have already answered that. But, as I have pointed out, in modern kettles the element is not in contact with the water.

It is true that the element is not in direct contact, but it is extremely close with intimate contact between the element and the skinny cover. The cover is only to reduce furring of the elements and has no other function.

The saucepan on the hob is quieter because it is made of thicker metal (which acts to absorb some noise) but also moves the water further away from the heat source.

The wider surface area of the saucepan base spreads the heat over a wider area (so is less intense thus lower energy cavitation) and the wider surface area lets more heat escape. Because of the distance between the heat source and the saucepan base, heat leaks away.

A hob is typically around 50 – 55% efficient providing you have the correct size saucepan on the hob. A kettle is close to 100% efficient because the element is in intimate contact with the water and little heat escapes the source other than into the water.

Cavitation is the formation of cavities – sometimes bubbles, sometimes voids – in the water close to the intense heat source. When these collapse (implode), they create violent shockwaves producing strong jets from the surrounding molecules. It is these shockwaves that you hear because water is a great conductor of sound.

In a saucepan, the water is heated far more gently, so cavitation is less.

(Sonic baths use the cavitation energy to clean objects. Ultrasonic sound is used to create cavitation and the implosion of the bubbles and voids cleans the surfaces around the object immersed in the bath.)

My suggestion is to attach the element to a thick aluminium base, possibly using the ‘printed’ element technology common in current kettles. That will add to weight, but for those who regard noise as more important than weight, it might be a good alternative. Insulation would help make kettles quieter and keep water hot for longer, albeit adding to their bulk.

Interesting to say the least! There’s little information from Kenwood but I’ve looked at about 50 reviews on various sites from UK to Oz and the many suggest that it’s not quiet or only marginally quieter than their previous kettles.

We’ll have to wait for Which? to test one.

Sounds like those “milk savers” glass/metal discs you used to put in saucepans to stop the milk boiling over. ( We are taking >50 years ago now)

I agree with Terfar’s list of desirable features for kettles, but add some extra points.

– Weight is an important factor for some, as has been mentioned earlier.
– Having an automatic switch-off that is both prompt and reliable is important. This is better than it used to be, but some kettles are still unsatisfactory.
– A flat, polished base is desirable for those who live in hard water areas. This may make kettles noisier but it certainly helps prevent build-up of limescale.

I also think it is time that insulated kettles were widely available, to help keep water hot. This will add to the bulk and weight, but these factors may not be important for many users. I would score insulated kettles highly for efficiency.

Durability is another important factor. When I was looking at the Kenwood website, I saw a statement that the expected life of a kettle is about five years. Top marks for honesty, but I would like to see all kettles with a manufacturer’s guarantee for ten years rather than one or two years. Our throw-away society is not sustainable and we need more durable products.

I completely agree with Terfar’s priorities.

We have not found recent Which reviews much help in choosing a kettle as the emphasis on speed seems to trump everything else.

The ability to pour cleanly without dribbling is critical, both for convenience and safety, and in my view Which does not give it the prominence that it deserves. I would not think this difficult to test properly and would like to know how Which tests and ranks pouring. If it does not pour properly it should be a ‘don’t’ buy or we are encouraging bad design!.

Having bought several kettles in the last few years which tended to generously pour boiling water all over the worktop (or occasionally splash my feet) as well as into the teapot, and being unconvinced of the adequacy of the current Which reviews, in desperation I bought the cheapest kettle in the local Waitrose. It pours perfectly, and apart from a slightly fiddly lid performs really well!

I still have one. Very useful when we have power cuts.

The usual explanation for the irregular noise produced by a scaled kettle is that steam is trapped under pressure below the limescale and there is a tiny explosion when it escapes. This is in addition to the noise produced due to cavitation when bubbles of steam collapse (this becomes less as boiling point is reached and bubbles of steam escape rather than collapse.

Boilers affected by limescale can produce worrying noises and central heating engineers refer to this as ‘kettling’.

This is your captain. Warning lights will be switched of shortly, but you are advised to keep your seatbelt on throughout the flight. As you have heard, the kettle has boiled and tea will be served soon.

go to sainsbury`s and buy one of there own make,on special offer,made in china.

I guess that you design kettles for a living.

Look at the Which? reviews and I think you will find the main strengths and weaknesses of kettles listed, David.

One of the problems is that companies introduce new models without adequate testing. I expect that the kettles that don’t pour well have replaced models that are satisfactory in this respect.

What concerns me is the safety of plastic kettles. Putting a powerful electric heater in a plastic container is asking for trouble, in my view, whether it is a kettle or fan heater. I would like to know if plastic kettles are a fire hazard or give off toxic fumes if the overheating cutout fails.

I suggest contacting the manufacturer if you spot problems and posting comments online, as we are doing here.

Hi wavechange. The problems that I know of, in the use of plastics in kettles are:

Potential leaching of plasticisers into the water with unknown health effects (I prefer to buy bottle water in glass bottles for this reason)

The plastic itself might add to the fire (as a fuel) or get burnt up without adding energy. eg If you burn PVC you can make small amounts of Dioxine although it does not add to the flames, but I doubt that PVC is used in food containers for this reason.

I am planning to write to Bosch about my kettle, so maybe they will listen and produce a better product in future.

David, I pretty much agree with Wavechange and your conclusions.

The ‘plastic’ electric kettles are made of fire resistant material. But the kettle is unlikely to start a fire. It doesn’t just rely on the auto cut off when it reaches boiling, it also has a second ‘over-heating device’ usually called ‘boil dry’ cut off. So from a fire perspective they are probably safer than some earlier generations of kettles.

I’ve always been a little concerned about plasticiser leach and for that reason I never leave water in my kettle. I always fill with fresh water from the tap approximately what I need and always empty the dredges after I I have finished. (This both ensures that the water still has the maximum dissolved gases and minerals for a good cuppa and that furring is minimised because cooling water isn’t left standing in the kettle.) I never buy bottled water, so that aspect doesn’t concern me.

What the manufacturers need to do is to stop making kettles using the principal of design over function. As I said in a previous post, the important criteria are comfort, filling, pouring and efficiency. If any of those are wrong, then the kettle is woefully inadequate. IMO, the other functions such as speed, noise and looks are quite secondary to the basic requirements and everyone will have different priorities over those.

One conclusion I can draw is that from reading Which? and other reports and reading users’ reviews, there is no perfect kettle: they all have a failure rate regardless of cost. It is difficult to judge the real failure rates because people naturally tend to report dissatisfaction far more than satisfaction (why praise something that does what it is suppose to do!).

David and Terfar

I do hope that ALL plastic kettles are made of fire-resistant material and that it does not produce toxic fumes if it is overheated. A kettle normally contains a 2 – 3 kW heater, which is a great deal of power to dissipate if something goes wrong. 🙁

I hope that branded kettles are either made of unplasticised plastic or made using plasticisers that are safe for food use.. That might not apply with some of the cheap kettles on the market.

If a kettle is switched on when it is empty, it will not shut off in the normal way because there is no steam. The modern kettles I have taken apart have only a single self-resetting thermal cut-out. These work like a crude thermostat and it is well established that this sort of cut-out can fail if contacts weld together as a result of arcing during operation. What there should be, of course, is a thermal fuse, but these are non-replaceable by the average householder. Forty years ago it was common for kettles to eject their power connector if they overheated. That was probably more reliable and in these days, kettles were made of metal. Kettles are often listed among the appliances responsible for house fires, but I have not seen numbers.

I used to make oxygen-free water for biochemical research in my university lab. Simply bringing water to the boil expelled the oxygen, so I reckon that it is a myth that freshly boiled water contains oxygen. Maybe the mineral content is different in freshly boiled and reboiled water, but I did not measure that.

I always leave [or put back] about a cup full of water in the kettle after use as a precaution against it being switched on accidentally when empty – it is so easy to do that with the base-level flip-switch. I see Terfar’s point about avoiding limescale build-up but I feel that is a minor annoyance compared to the risk of boiling when empty as Wavechange has explained.

I leave surplus water in the kettle or fill up after use, for the same reason as John has given.

I have not carried out tests but suspect that most of the limescale will have been deposited by the time the water has boiled. Limescale is much less of a problem with a kettle with a shiny stainless steel base. Most of it accumulates as a coarse powder that can be emptied out.

I have to be careful here not to panic everyone. About Dioxines (chlorinated dibenzodioxine family); they are pretty nasty organic materials that can cause cancer, but fortunately they are usually found in very tiny amounts. They and other related organics like chlorinated dibenzofurans, can be produced when chlorinated materials such as PVC are burnt, so you should never burn these; although the clean up of a building site when the work has finished, often includes a bonfire rather than a skip which is bad practice because the rubbish usually contains scraps of PVC pipe and electric conduit.

So don’t worry about dioxines and kettles, because any plastic is unlikely to be PVC and it doesn’t get produced unless the plastic is caught up in flames. What gives more concern is the plasticisers added to the plastic to make it extrude more easily in production of the plastic parts.

It’s really nothing to do with noisy kettles but…

It’s an urban myth. As is the warning about freezing water in plastic bottles. Dioxins do not leach into bottled water even if the bottle is left in the sun in a car. There are still on going investigations into the leaching of dioxins into food and the current precautionary advice is:

Don’t use a plastic container to heat food in a microwave unless the container specifically states it is microwave safe.
Any cling film placed in a microwave should not be touching the food.

Dioxins are plasticisers: they are highly carcinogenic. Fortunately dioxins have low volatility and low water solubility ( http://www.atsdr.cdc.gov/toxprofiles/tp104-c3.pdf ).

Thank you, I was going to have asked about microwaving plastic. I know some people who microwave food in melamine plastic bowls.

Terfar – Dioxins are not used as plasticisers.

fl – I suggest you follow Terfar’s advice and don’t microwave food in any plastic unless it is intended for the purpose. Pyrex containers are ideal.

corrected my E/mail address,
yours Roy