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My tea preparation prescriptions says to prepare it using water heated to 96 Celsius degrees.

When water heated in standard, typical electric kettle reaches this temperature?

Is it (always?) immediately after switch turns off? Or is it 100 Celsius degrees, and I need to wait approx. 3-5 minutes to get to cool to 96?

  • And is there any discernible difference between the tea made at 96C versus 100C? – David Richerby Oct 21 '14 at 8:49
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    Ask those guys, who are responsible for writing "Use 96C water" not "Use 100C water". – trejder Oct 21 '14 at 14:03
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    When they say 96°C, I think it is safe to assume that you can boil the water and pour it straight on the tea leaves. Don't overthink, but if you do, get a cheap instant digital thermometer, I use one for green teas. – Max Oct 23 '14 at 19:24
  • I normally see tea vendors round with 5ºC so 100, 95, 90, 85 etc. It really doesn't have to be this exact. With 96, the vendors most likely means to just let the water cool down slightly. To reach 96, I would pour the water after boiling into a pitcher and then pour it into the teapot. – Lisa at Teasenz.com Jul 12 at 6:59
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Seconds, not minutes. Just the act of pouring the water will cool it slightly. At sea-level pure water will be 100C at a full boil, the temperature will drop immediately when it's no longer being heated.

This is unscientific at best, but just for giggles I put an accurate digital thermometer into a room temperature mug, and brought a couple of cups of cups of filtered (not distilled) water to a boil in a saucepan. I poured the water into the mug and held the thermometer in the center of the mass of water. In the time it took for my thermometer to stabilize on a reading (30 seconds), the water was at 92C.

I repeated the mini-experiment using a hot mug that I had heated by boiling some water in the microwave, and pouring it out just before I poured in the boiling water from the saucepan. This time after the 30 seconds it took my thermometer to stabilize, I got 96C.

I'd say that just by doing this (with a warmed ceramic teapot), you'd have your 96C if you moved quickly.

96

Photo from Instructables

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    I can confirm this (for coffee in a french press you need a similar temperature). Waiting for the water in the pan to drop down to the right temperature took several minutes, but I found that if I poured the water in a thin stream from relatively high up, it would be down to about 95 in the french press. This also means that if you want exactly 96 degrees, you should pour with a thick flow from low height so it's in the pot above 96 and wait for it to drop before you add the tea leaves. – Peter Oct 20 '14 at 16:20
  • I also did this experiment today. I poured some water boiled by an electric kettle to an unwarmed heat-insulated mug. The water temperature inside the mug was 92°C. – cartoonist Jan 18 at 13:27
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Basic electric tea kettles primarily work by turning off when a bimetallic switch in the handle (probably at the bottom, where it will require some steam pressure to have steam travel down to) of the kettle is sufficiently heated to deform one of the metals, turning off the kettle. This switch is heated by steam, and the element itself is typically turned off well below 100°C (closer to 85°, perhaps) to ensure it doesn't go on heating indefinitely, particularly well above sea level. This ensures it is boiling, as the steam pressure required to move the steam to heat the element doesn't exist until the water is at a full boil.

As such, you can't assume any specific temperature from the kettle without knowing your altitude, and most accurately taking the temperature yourself. It does not heat to a specific temperature independent of altitude/pressure and stop, if you're using one of the cheaper models; if you have a model that has digital temperature control, then of course you can simply set that.

Now, the temperature it stops at is quite stable, for your altitude; so if you determine that temperature (either with an accurate thermometer, or by searching the internet and/or doing the math to find out what temperature water boils at where you live) it's likely very consistent. So if you are looking for 96°C, and where you live water boils at 98°C, you can work out how to drop it those two degrees pretty easily.

Example information: UK Museum of Science and Industry article about Kettles

John Taylor, one of the early inventors of this kind of switch

Russell Hobbs, another UK company that pioneered this process, and includes some information as to how it works on the page:

The automatic electric kettle K1 (a world first), designed in October 1955, used a bi-metallic strip at the rear of the kettle: steam was forced through an aperture in the lid of the strip and this knocked the switch, turning the kettle off.[3]

(I can't source that actual statement, as [3] doesn't go to a page that uses this language, but it's within reason compared to other similar pages.)

  • I just looked on Amazon. Every single electric kettle in the top 5 sellers claims to boil water. The one I had in college, many moons ago, certainly did. I used it for ramen, and I remember clearly. – Jolenealaska Oct 20 '14 at 22:54
  • Typical-"The Ovente KG83B Black is a high class glass designed electric kettle that looks great on any kitchen or countertops. With 1.5 liter water capacity and 1100-watt of power -- this electric kettle can quickly bring water to a rolling boil. It is proven to be 85 percent more efficient than stovetop kettle that can reduce your daily electricity use." That one is glass, you can see the water boiling. – Jolenealaska Oct 20 '14 at 23:02
  • Where did I say it wasn't boiling the water? The element turns off at 85 degrees, but that's because it's nowhere near the water. It's being heated by steam, and turns off when it hits 85. The water has to be boiling to produce that amount of steam. – Joe M Oct 21 '14 at 0:53
  • @Jolenealaska Updated the answer to make that more clear hopefully. – Joe M Oct 21 '14 at 0:58
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    @Jolenealaska Actually, altitude is relevant. If you live at about 1,200m (4,000ft), water boils at 96C so will have cooled below that however you pour. Almost the whole state of Colorado is above 5,000ft, where water boils at 95C and it's impossible to make tea with 96C water. – David Richerby Oct 21 '14 at 8:54
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Assuming your kettle causes the water to boil (rapid escape of gas/bubbling) and that the water you are using is from a tap (not distilled) then it is very difficult to say exactly the temperature of your water at boiling, but it will be a small amount over 100 Celcius degrees (as impure water has a higher boiling point).

To know when your water has reached 96 Celcius degrees, you will need to use a thermometer to test for the exact temperature, which can be reached quicker by pouring into a cool container or pouring between containers.

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    The level of dissolved material in tap water will make no discernible difference to the boiling point: fractions of a degree at most. Altitude is probably more significant: every extra 300m above sea level cuts the boiling point by about 1C. – David Richerby Oct 20 '14 at 20:59
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Pure water boils when its vapour pressure equals atmospheric pressure. Pure water will only boil at 100 degrees at sea level if the atmosperic pressure happens to be 1 atmosphere (760mm of Hg)

The boiling point of water therefore depends on two things. 1. How pure it is. 2. What the atmospheric pressure is where the water is being boiled.

In general terms the higher you are above sea level the lower the atmospheric pressure. Atmospheric pressure also changes daily with the weather systems passing through.

It is extremely unlikely therefore that you will ever get water to boil at 100 degrees Celcius.

If you live 4000 feet up the side of a mountain and it's a low pressure day your water will boil below 96C

  • The question isn't just about the boiling point, but about how fast it cools off once it's no longer actually boiling since the heat source has been removed. – Cascabel Oct 21 '14 at 5:55
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Electric kettles regulate their set temperature with either a thermocouple or a resettable thermal fuse. Both devices are likely good to within 10% of their nominal value, and are affected by the amount of lime scale on the bottom of the pot. That means that the only way to be sure is with a thermometer; used not just once, but every week or two.

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    But...but...if the water is boiling, it's boiling. – Jolenealaska Oct 20 '14 at 14:15
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    @Jolenealaska -Some of these heaters are designed to just get very hot, without actually boiling the water. Those are the type I'm talking about. Yeah, boiling is boiling hot, unless you're at 4000 meters. – Wayfaring Stranger Oct 20 '14 at 14:25
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    I'm sorry but this is nonsense. Every electric kettle I have ever used has heated the water until it is boiling vigorously and then stopped. As @Jolenealaska says, when it's boiling, it's boiling and the temperature that water boils at is 100C at sea level, minus about 1C for every 300m of altitude. – David Richerby Oct 20 '14 at 21:03
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    @WayfaringStranger That's not an electric kettle, that's a drip coffee maker. – Jolenealaska Oct 21 '14 at 2:25
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    @DavidRicherby I had one, used it for making tea 70's through 85 or so, when it crapped out. Now I use a kettle on the stove. Perhaps it was a rare device. – Wayfaring Stranger Oct 21 '14 at 13:14

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