For this black matte colour, it is typical for one to notice a reddish coloured ring at the rim of the pot. This happens as a natural result of the pottery process and is called "suri-awase" in Japanese which is done to appropriately piece the lid and pot together. The red colour simply reveals the clay’s original colour.
As the teapot is used, the surface of the teapot's colour will slowly deepen overtime. The built in hand crafter strainers are at the base of the spout which works as a strainer.
Material: Ceramic (Clay which is high in iron content)
Detergent for cleaning is safe. Please refrain from using sponges with abrasives, metal scrubbing brushes, cleansers, etc. Avoid washing the inside of the teapot with your bare hands.
If you are concerned about tea astringency, soak it in diluted tableware oxygen bleach overnight to clean it. Be sure to soak it in tableware bleach, wash it, and dry it completely before storing it, especially for a long period of time.
Do not be warned if there are black spots on the surface. It is the colour of the natural minerals contained in the clay and it contains iron powder.