Excerpt:

Tatsuo explained how the behavior of steam in the yuzamashi (water cooling pitcher) can indicate temperature. Steam billows upward with near-boiling water temperatures, ideal for hojicha or bancha. Water at temperatures around 140°F will have little or no steam, ideal for gyokuro. Steam moving to the side at an approximate 45° angle indicates temperatures around 175°F - 185°F, ideal for sencha.

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