If you don’t have a thermometer, don’t worry. There’s an old Chinese method for achieving proper temperature (that is still very much in use today) that teaches you to determine temperature through visual observation of the water in your kettle. Follow this guide:
Shrimp Eyes: When you first start seeing small bubbles the size of shrimp eyes at the bottom of the water, the temperature is 155–165°F.
Crab Eyes: When you see slightly larger bubbles the size of crab eyes and small wisps of steam are starting to rise, the temperature is 175–180°F.
Fish Eyes: When you see bubbles the size of small pearls (or fish eyes) and there is noticeable rising steam, the temperature is 185–190°F.
String of Pearls: When you see bubbles briskly streaming to the top in continuous strings like a pearl necklace, the temperature is 195–205°F.
Raging Torrent: When the water is bubbling violently in a rolling boil, the temperature is 208–212°F.