3rd topic: how tea impact the clay hence improves tea itself - why raise a clay teapot?
Now that we have an idea what clay can do to tea, what can tea do to clay? Dissoluble substance of a leaf as we can observe is not colorless. Tea stain is dried such dissoluble substance. We can smell aroma of such substance dissolved in water, we can taste the sweetness/bitterness/astringency of such substance dissolved in water. Fragrance is from distinctive essential oil of a plant. Lavender oil, rose oil or tea oil are all essential oils of its own species. When dissoluble substance and oil are released from a leaf into water inside a clay pot, sip through tiny air hole among clay, when dried, the substance stays in the pores (storage cabinets). More usage of the tea pot the more deposits will be stored away. Polishing a pot is to evenly distribute these essential oil, hence the shine on the exterior. This is cosmetic enhancement of the clay pot appearance.
It's commonly known to use one pot for each specific type of tea, similar in flavor and roasting method. The logistic is to accumulate similar substance in "storage", when making tea, these deposit will be redissolved again some what, hence enhance the tea flavor and aroma. Kinda like cooking a chicken with chicken broth. It's not a myth that a well used clay pot can make fragrant tea with only water. Ceramic and glass wares are not porous materials, therefore can not store away these flavorful substance, neither can they neutralize or react chemically with tea, therefore they can not enhance nor diminish tea flavor, however reflect true flavors.
These 3 articles briefly explains why the need or desire to raise a clay pot. The next article will talk about the techniques in raising a pot.