Is the Best Water Temperature for Coffee 30-seconds Off the Boil?
A quick Google search comes up with numerous articles stating that the correct water temperature for brewing coffee is between 195- and 205-degrees.
The question becomes (at least for those of us that don’t have an electric variable temperature teapot) when to add the hot water to the coffee grounds without scorching them or under extracting the coffee?
A search of competent websites gave a range of between 30- and 90-seconds once the water has boiled and been removed from the heat.
Not that I don’t trust people, but if I can easily check the facts for myself I’m going to see if they’re right.
Since most of the reference articles just throw the 30- to 90-secs out there without stating how much water to heat up or if you should leave the teapot closed or open, I figured I’d find out for myself.
Below is data I collected and my recommendation for the volume of water to heat up and how long to wait before the water temperature for coffee is in the ideal range.
This is the first in a two-part post as there is another step to experiment with before the ultimate question can be answered.
Why I Tested The Consensus
Let’s face it, in the morning I want my coffee, and I want it now!
So, why heat up more water than I need?
It will only take longer to boil.
But will a smaller volume of water stay warm enough long enough to brew good coffee?
Or is it better to use a larger amount of water, so it stays hot longer?
I need to find out.
When we make a pour over coffee or use a French press pot, we need to heat water, and unless we go to the extreme to put a thermometer in the teapot, the only temperature benchmark we have is boiling water.
So I knew water first had to come to a boil and the questions I had to answer are:
- Does a small volume of water cool too quickly and under extract the coffee?
- Will a large volume of water cool too slowly and scorch or over extract the coffee?
- What is the best way to cool the water, leave the top on the pot or remove it?
- How long of a window do we have before the water is too cool to extract enough flavor from the grounds?
How The Test Was Done
The idea was to see how fast two volumes of boiled water cool over time.
For the water volume, I decided to use 4-cups and 7-cups. The only reasoning was that using more than 7-cups in the teapot allowed water to boil out of the spout.
Using any less that 4-cups of water in the pot and was hard to secure the thermometer without touching the bottom of the teapot.
The teapot was an inexpensive thin-walled stainless steel vessel that holds about 8-cups when filled to the bottom of the spout.
It’s your average $10 to $12 teapot. Nothing fancy. If you own a more robust metal teapot, I would expect a slower decline in temperature than what I show.
The opening at the top is 3-inches in diameter. For the testing, I used the same water volume twice (refilling between tests), one with the top on to retain heat and the other with the top off to release heat and steam.
To record the temperature in the closed top test, the probe of a digital thermometer with an accuracy of ± 1° was inserting into the steam whistle. For the open test, I secured the probe to the handle. For both trials, at a minimum 1-inch of the probe was in the water.
Once removed from the heat, the teapot rested on a wooden butcher block covered with a tea towel.
I recorded the water temperature at 15-second intervals from boiling to the 10-minute mark or 180°, whichever came first.
Then I plotted the recorded data on a graph of temperature verse elapsed time from the boil.
Below is a graph of the recorded data.
The cooling patterns between the 4- and 7-cup tests are similar. Water cooled more rapidly with the top open compared to the top closed. And the larger volume of water cooled slower than the corresponding smaller volume of water.
I believe anyone would have expected those results.
The 4-cup, open top test (red line on the graph) is approaching temperatures too cool to properly extract coffee from the grounds. This is because the grounds, filter, and French pot will also cool the water as it’s poured into the vessel.
From these data, it appears that the other three tests could still produce a proper water temperature for coffee brewing.
However, it remains to be seen if it’s necessary to cool a full pot of water with the top on for a couple of minutes before pouring it over a bed of grounds.
Because the temperature was still around 209-degrees for 3-minutes and remained hotter than 205-degrees for 8-minutes.
In the next test, I will measure the temperature of the coffee slurry over time as hot water (7-cups & 4-cups with the top on) is poured over the grounds in a pre-heated Hario V60 and a 1-liter French press.
By the end of the next test, I’ll be able to tell what volume of heated water is best to supply the correct water temperature for coffee brewing.
Data from the next test should also help decide the what the temperature setting should be on an electric variable temperature kettle.
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