I went to Marukai Market with my parents today and was quite taken with a $422 cast-iron teapot they were selling in the kitchenware aisle (among other wonderful things: a tiny miso whisk, a panda onigiri set complete with a panda silhouette nori punch, a homemade mochi maker). It was locked in a glass case and you needed to call an associate if you wanted to purchase it.
The sign posted next to it claimed that water boiled in the Tetsubin (Japanese Cast Iron Kettle) gives tea a more mellow, sweet taste. Here’s more from a website called Hojo Tea:
The chemical structure of water is part of the key that explains how water changes when boiled in a Tetsubin. The water molecule (H2O) consists of two elements, hydrogen (+)and oxygen (-).These elements carry both positive and negative electrical affinities or charges, just like a magnet. This is called dipole in Chemistry. These equal electrical charges, that exist on both oxygen and hydrogen, cause water molecules to constantly spin when in a liquid state . If they stop spinning, then water will become ice. Variable intensity of hydrogen bond allows the flavor and texture of water to change depending on the instrument utilized when boiling it. For example, if there is no mineral content in the instrument utilized to boil the water, for instance, a sterile glass beaker, the positive and negative charges of the elements of the water molecule will simply be attracted to each other and form their network or molecule through their hydrogen bonds. These bonds give water it’s characteristic viscosity and surface tension, but a plain or flat flavor. However, when minerals exist in the instrument utilized to boil the water, for example, the Tetsubin, the elements of the water molecule are attracted to the minerals from the Tetsubin instead. In fact, the affinity of the water molecule with certain types of minerals in the Tetsubin is stronger than those existing between the water molecules themselves. Minerals and water molecules form more stable bonds. This stronger attraction between minerals and water molecules also increases the viscosity and surface tension of the water. This effects our perception of the flavor and texture of the water itself, and most importantly, our taste buds can feel more taste, and a taste that stays longer in our mouths thanks to the stronger attraction of these hydrogen bonds and the metal ions of the Tetsubin.
The presence of minerals also affects the depth of the water’s flavor. Minerals attract volatile flavor producing substances and form stronger hydrogen bonds in water. The stronger these hydrogen bonds are, the slower the evaporation of such volatile substances becomes. As the result of slow evaporation, we feel a much deeper and longer lasting flavor in our mouth.
Very interesting! I’ve only used these heavy kettles in a few restaurants. They do keep the water extremely hot for long periods of time.