Wednesday, May 11, 2011
Harmonizing Water and Tea: Part 8- Scaling and Other Issues With Kettles and Tetsubins
It is known that leaving scale to develop inside your kettle/ tetsubin will improve the taste of the water and the tea steeped with this water. Nowadays scale gets such a bad rep but long ago teamasters prized the scaling on their tea implements deeming its formation as necessary to ensure the harmony between water and tea. The white precipitate adhering to the inner walls of the kettle was likely an indication of the qi of the water interacting with the qi of the boiling vessel. Essentially it reveals the connections between Heaven and Earth. The colour white is considered the colour containing the most heavenly qi. A white substance that appeared in their kettle after use was therefore considered a good and maybe even auspicious sign.
It is true that such scaling doesn't occur overnight. Just as it takes years to cure a tea pot, it also takes years to develop a nice layer of scale on a kettle. Hobbes from The Half Dipper has been documenting the scaling of his iron tetsubin here, here, and here. This is another reason why scale is prized in kettles just like a nice patina on a tea pot is also valued.
It was mentioned in Part 6 of this series that the boiling of water is one of only two instances in the preparation of tea where three of the Five Elements converge. From this perspective the emergence of scale is caused when the interaction of Fire and Water takes place within Earth or Metal. The Fire Element is thought to strengthen Earth as the water boils for tea. The minerals in the water are Earth and when under the intense heat of the fire they are thought to be strengthened and form scale. Conversely, the Water element is thought to control Earth. When water that was boiled begins to cool the minerals of the water are isolated and are left behind in the kettle/ tetsubin.
Scientifically, these two methods of scaling can also be defined. When scaling occurs due to water that is heated, it is due to the minerals in the solution having retrograde solubility. When scaling occurs due to water cooling, it is due to minerals in the water that have normal solubility. The mineralization or heaviness of the water plays a role in the scaling of a boiling device.
The chemical make up and porousness of the materials of the boiling vessel also influences the amount and type of scaling that will occur. The chemical make up of the vessel impacting scale development is referred to as chemical reaction scaling and occurs often as metals act as catalysts in the reaction to form scale. The porousness of the boiling vessel also plays an important role in the formation of scale. A more porous vessel such as ceramic would allow the formed precipitate something to anchor itself to where as a very smooth material such as glass would simply allow the formed precipitate to exit the boiling vessel into the tea pot.
Heat plays an very important role in the chemical reactions that take place. The qualities of the heat source such as the intensity, evenness, and speed of the boil therefore affect the development of scale.
The formation of scale is due to an interaction between the heat source, the mineral content of the water, and material and properties of the boiling vessel which is containing the solution. This is true for both modern scientific and traditional theoretical points of view.
Either way what develops is scale. Scale is thought of as a manifestation of the Earth Element. Earth is harmonizing and regulating in nature and therefore imparts certain regulating properties to the water. Essentially it removes the harsher edges of the water and augments the softer qualities. It is true that an increase in metallic impurities such as sulphur as well as valued trace elements increase scale development. Therefore a chemical buffer is created which moderates and harmonizes the properties and chemical make up of the water (see Hojo's commentary on water).
The white colour of the scale connects the tea maker (Man) to Heaven and Earth. It also is an indication of the general strength of the reaction between Elements and an indication of the qi of the water. Scientifically, the presence of oxygen also impacts the development of scale. Historically, many parallels between Oxygen and Qi have been drawn. The oxygenation of water speaks to the source, how fresh and vibrant it is, as well as how it was stored and poured, therefore all of these factors will impact scale development.
The topic of using the kettle or tetsubin to store water should be mentioned here as well. Most metal kettles/ tetsubins such as those made of silver and iron should never be used to hold water unless it is to be immediately boiled. If water is left in these kettles they will tarnish and rust and the metallic taste will leach into the water. However for kettles and tetsubins made of earth or glass this is not the case.
Although glass won't impart negative qualities into the water, because it is transparent any light will degrade the water. Leaving water in a glass kettle is not really recommended. Some tea masters claim that leaving water in a ceramic kettle overnight before boil will reinforce the harmony between the boiling vessel and the water and lead to a better tasting tea especially for those teas that harmonize best with ceramic kettles. In many ways water that rests in a ceramic kettle/tetsubin is enhanced the same way that it would if it were stored in a water storage container. Conversely, others feel that freshly poured water into the kettle is somewhat more vibrant than water which has been left stagnant.
Lastly, it may also be worth considering where the material of the kettle/ tetsubin comes from. If the material is from the same area as the water that will boil inside of it and from the same area as the tea that will steep in this water, quite naturally, greater harmony between the tea, water, and kettle/tetsubin will be achieved. The result will be a much more satisfying cup of tea.