Temperature

The temperature of the water you use to make tea is all-important, particularly for the more delicate green and white teas (black ones and herbals are more robust so can withstand boiling water). Too hot and the tea will swiftly become bitter and astringent, too cool and the leaves won’t release their flavour and colour properly, particularly if they are tightly twisted or rolled varieties like jasmine pearls, for example.

I’m not generally too fussed about measuring temperature exactly; usually what I do is bring my water to a full boil in the kettle and then decant it into something else, like a jug or my glass teapot, to cool. Sometimes (if I’m feeling adventurous) I will pour it from cup to cup a few times - this has the advantage of cooling it more quickly and also warms the cup or mug I’ll be drinking from, but the disadvantage of making it slightly more likely that I will scald myself. I think I might have read somewhere also that this method ‘aerates’ the water, restoring some of the oxygen that got lost in the boiling process, but who knows whether this is actually the case – certainly not me! Could well be one of those urban tea legends…

So I don’t normally resort to using a thermometer to determine when my water has reached the right temperature for the tea I’m brewing. However, last night I decided to brew up a new green tea that I had waiting in the cupboard (more about the tea itself in another post) and thought I would take the scientific approach instead of the slapdash haphazard one.

I was surprised, when I poured out the amount of freshly-boiled water (just under a metric cup) and then placed the thermometer in it a few seconds later, that the temperature that registered was only about 75°C* (that’s about 170°F for all you imperial readers out there). I didn’t think that the water would cool that much in the short interval – space- and time-wise - between the kettle and the jug. I placed a second thermometer in the water and it registered only up to about 60°C while the other was still on about 70°C.

So I am rather confused. Is my kettle not actually reaching boiling point? Is one of the thermometers wrong, or are they both inaccurate? Does a relatively small volume of water cool much more rapidly than I would have expected?

More experiments will have to be conducted, and more tea drunk. Mmm… need more data.


* serendipitously, this was just about the exact temperature of water that I needed for this tea.