All good domestic electric kettles evaluate the water temperature in some way - typically to switch off when the water has reached the target temperature[1]. Most are designed to give a clear indication when they achieve this state, for example switching off with an audible 'click'.
Nowadays, many kettles also include LEDs to indicate that the kettle is 'on'. These are ubiquitously single colour - at the moment the trend is to use blue as an 'on' indicator for all electronic devices. However, I see this as an opportunity missed.
Variable temperature kettles exist. You can specify the temperature to which they will heat water. However, as far as I could determine, these all use a small LCD display to show the desired (and/or possibly current) temperature.
I'd like a kettle which uses colour-changing LEDs [2] to indicate the temperature of the water in the kettle. Blue would be cold water, 10 degrees C or lower. Red would be 'boiling' hot water at 100 degrees C, and there would be a human-adapted spectrum in-between[3]. This way, you could judge the kettles progress, and remove it early if you wanted cooler than boiling. I'd also like the ability to see a report of the current temperature without heating the water. One option to provide this feature would be to use another button.
Yes, this will require additional electronics and make the kettle more expensive. Probably not prohibitively so.
[1] I used to have a kettle which lost this ability. Mister Boily, I called it. [2] Actually, multiple different wavelength LEDs in a single package - this isn't important. [3] Following a 'linear' hue scale over the temperature range may be sub-optimal - we want to maximise the discrimination so that users familiar with the device can accurately judge heating progress, and when the water is the temperature they prefer.-- Loris, Oct 13 2022 Smart Kettles https://www.pocket-...-best-smart-kettlesNow they are smart, what can they do? Oh, yeah, boil water. [mylodon, Oct 18 2022] //Why even use lights? Use a thermochromic element - akin to a mood ring but calibrated to the right temperature range.I found you a (link). Is that close enough to what you want?//
I see from the comments that this has various issues with the colour-changing paint - in particular, changing colour less with time. But even assuming those could be fixed, I'd say it's not quite there. Watching the video, it transitions from black to red at a critical temperature, which isn't enough. I want a display indicating position within the temperature range, not a binary state. And ideally utilising a wide gamut of colour. My (very cheap) kettle has blue LEDs to show it's on. Very cheap colour-changing LED night-lights etc. are widely available. Kettles which can set the temperature exist. It's really just a merge.-- Loris, Oct 13 2022 You can get colour-changing pigment themometer strips already. They're not very good. If you really insist on not using lights, you could just use a thermometer. But while it's better than the colour strips it still doesn't have the ease of use I was aiming for.-- Loris, Oct 13 2022 Regarding your "The very thing!" link - that certainly looks the part, and there is an image which has the kettle lighting up in different colours at different stated temperatures. And the description states "Electronic temperature control features easy presets, as multicolor LED illumination adjusts according to preset temperatures." If that's the case, it's pretty much what I was describing.
However, I'm a little bit suspicious. The images are obviously recoloured versions of the same image - the BOIL image doesn't have additional bubbles, which is a bit of an oversight. That's not necessarily nefarious - it's pretty hard to get images of some things, and 'photoshopping' is common in advertising to get an image which "looks like it does in real life" without the intention to mislead. Also, there is some sort of protrusion inside the base which could be a temperature probe.
So I was considering getting one to find out, but it's the wrong voltage.
So then I tried searching, and haven't found a UK version - although there do seem to be numerous similar-looking kettles which the listings seem to indicate cycle through the colours. Perhaps aesthetically pleasing, but not what is required. I tried the model number, and found an Amazon listing for the kalorik kettle - still the american form, and it said: "5 different colors according to selected temperature". Looking at the image of the handle back on the original listing, there are four LEDs with different temperatures, and plus/minus buttons to switch between the selections. The original listing also says "Electronic temperature control features easy presets, as multicolor LED illumination adjusts according to preset temperatures." Which I hadn't quite appreciated, but now seems clear.
So it lights up according to the temperature you've selected when it's done, or something like that. It's a near miss.-- Loris, Oct 13 2022 Your "Yet another" link is doing the same thing, but with different temperatures.
They're not doing what this idea describes.
(added in light of cross-posted comment above)
// I'm curious enough myself to order one from Amazon just to find out.//
Thank you - that's very good of you. They do look like nice kettles, anyway.-- Loris, Oct 13 2022 I've just found some uk-suitable colour-changing kettles on amazon - supposedly blue to red as it boils, then back to blue. But they're getting destroyed by reviewers.
Here is one: "Its looks nice but a bit disappointing not exactly colour changing... Light remains blue when it is off and turns red when its on. Then immediately returns to blue when it reaches the boil. I was expecting use if available tech where it gradually turns from blue to red and gradually returns to blue when cooling. Underwhelming is how I would describe it like a giant coloured on off button."
another: "The BLUE led is on - all the time - unless you switch the kettle off at the wall The RED led comes on when boiling The LED's are a bit of a gimmick though - and not particularly well done - after about 3 weeks the switch from Blue to Red started to fail and the kettle gave off a purple mix of the 2 while boiling"-- Loris, Oct 13 2022 Those Bastards!-- 2 fries shy of a happy meal, Oct 14 2022 I have a bluetooth toothbrush.
I find everything is bluetooth now. Harold must be proud. Or rolling over in his flaming canoe.-- mylodon, Oct 18 2022 random, halfbakery