This series of posts started from a fairly simple question in my head – what is the rate of cooling of water from boiling – to have some sense of what temperature coffee making is conducted at when there are no thermometers to hand! It has turned into a rather more complex investigation than first thought – but has been at least a little fun along the way. Here, were close to the end of my write-ups!
We’ve already covered that when transferring water after boiling from an electric kettle into another vessel such as a Buono kettle (in order to achieve greater accuracy for pour over coffee making) there seems to be about a 3 or 4 degree Celcius loss of temperature straight away.
So this post is about the expectation that as the water is then poured from the Buono onto the coffee grounds themselves there is likely to be another (notable?)drop in temperature.
That was the expectation and indeed has been exactly what I observed in my experiments.
In order to attempt to measure this effect, I rigged up a set-up (imperfect, but trying to get close to something realistic) where I could pour water from the Buono spout directly onto the bulb of the thermometer. That’s the closest I’ve been able to construct to something reasonably meaningful.
I conducted most of my previous efforts over a 10 minute observation window – however the idea of pouring water from a Buono kettle for 10 minutes was never going to be achievable – I did try and control it well, and managed around 5 minutes each time, which I think was a good achievement (also meant my rate of pour should have been similar on each attempt).
The temperature within 30 seconds had dropped to 90 degrees Celcius, but took till almost 6 minutes to drop the next 5 degrees – by which point it was almost equal to the observations of the temperatures achieved in the Buono kettle itself(with no pouring).
That line on the chart that resulted did puzzle me at first – although the greater initial drop in temperature made sense, the slower rate of decline in the following minutes than observed in the kettles did seem odd ( I haven’t worked all the way through this yet, but I think one of Newton’s Laws does help – I need to look into that a bit more, and will try and write something in a few days).
What also seemed odd is that the water poured from the Bouno (having been poured in the Bouno from the electric kettle) was at a lower temperature in the earlier moments of observations than the water in the open-top vessels.
OK – only for 30 seconds, but that it crossed the line, then crossed back again made me think that this science lark was just far too complicated!
But here could perhaps be the most important thing to understand from these experiments – that the pour itself is where the temperature changes the most (pouring from the kettle used for boiling, into another vessel in the first place, and from the pouring vessel onto the coffee).
And therefore different styles of pour, durations of pour, or methods of dealing with the water will mean that the temperature, in effect, on the coffee is different.
This is where the water is coming into most contact with the air (or perhaps more importantly (scientifically) the much lower ambient temperature) and so is losing the most heat.
So I guess one of my biggest conclusions is that when we’re talking temperature we may or may not be talking the same thing – the temperature of the water can change greatly quite quickly depending on how it is transferred from the boiling vessel to the coffee.
Water that is the same temperature for 2 different coffee making techniques at the starting point could actually be at very different temperatures when hitting the coffee grounds seconds later.
This coffee making really is both an art and a science!!
please note: boiling and hot water can be dangerous if not handled with care!
(despite the haphazardness of some of my approaches above, I did take some care and would suggest anyone else does the same: and children should be accompanied by an adult)