A Quick Guide to Water: Estimating Temperature, pt. 1

March 31, 2020

by Jessica Maciuch

If you’ve ventured into the world of green, white, or oolong teas, you’ve almost certainly encountered the golden rule of brewing: NEVER use boiling water. For more delicate teas, such as Japanese greens, water temperature determines the balance of bitter and sweet flavors that are brought out of the tea. The last thing you want is to sit down with a cup of gyokuro, only to realize that the water was way too hot, and you’re left with the flavor of scalded tea leaves instead of those prized notes of umami. But what if you don’t have a thermometer on hand, or one of those programmable electric kettles?

Fortunately, you have an easy option for how to estimate water temperature with nothing but a pot of water and a heat source. This method has been used for hundreds of years, and relies on gauging the size of the bubbles forming in a pot of water as it heats up. To use this method, you will need to be able to see the water as it boils. You can either use a glass tea kettle or just a regular saucepot. Note: If using a glass kettle, please be sure that it is made to withstand direct contact with a stovetop!

In Record of Tea, Cai Xiang, a Chinese writer and intellectual from the Song Dynasty, identified 5 distinct ‘stages’ that each correspond to a specific temperature range.

Stage 1: Shrimp Eyes

The name of this stage references the small bubbles (approximately the size of the tip of a bobby pin) that appear along with the first wisps of steam. At this point, the water is around 155-165°F (68-74°C). This is the correct temperature for the most delicate green teas, such as Shincha (First Harvest) Sencha.

Stage 2: Crab Eyes

The bubbles have slightly increased in size, and they begin to noticeably ‘wink,’ as shown in the image below. This stage corresponds to temperatures between 170-180°F (77-82°C). Use water at this stage to brew most Chinese green teas, like a classic Dragonwell.

Stage 3: Fish Eyes

At this stage, larger bubbles will reach the approximate size of a green pea. Water reaches this point between 185-195°F (85-90.5°C), making it ideal for most green oolongs, such as Tie Guan Yin.

Stage 4: String of Pearls

As the name implies, this stage is characterized by steady chains of bubbles from the bottom of the pot to the surface. This fourth stage begins once the water reaches approximately 205°F (96°C). I personally like to use water at this temperature to bring out the sweet cocoa notes of less oxidized black teas, like Yunnan Golden Curls.

Stage 5: Raging Torrent

This is what most people picture when they think of “boiling water.” At this point, the water has reached 212°F (100°C), and is ready to use for hearty black and herbal teas.

Once the water reaches the correct temperature, it’s time to brew your tea! Keep in mind that water will drop in temperature once you transfer it to another container. For tips on how to account for that, check out the second part of this series on estimating water temperature.