Tezu is a very weak vinegar solution made from water, rice vinegar and salt.
It is used when making sticky items such as sushi, mochi or omusubi.
In making sushi, it is used to wipe the insides of the rice bowl (Sushi-oke) before starting, to dip your fingers into whenever they start to get sticky during the assembly process, and to wipe knives off whenever they start to get sticky,
Rarely, you may see a Western-written recipe for it that doesn’t call for rice vinegar, but the overwheming majority call for the vinegar to be added. Besides, the “zu” part of the word “tezu” means “vinegar.”
Rarely as well, you may see a suggestion that equal parts of vinegar and water should be used, but that seems to risk imparting too much of a vinegar flavour.
Occassionally, Tezu is confused with a stronger-flavoured solution that is meant to be poured into the cooked sushi rice to season it. That solution is called “sushi-zu.”
1 cup (8 oz / 250ml) water
2 tablespoons rice vinegar
1 teaspoon salt
Cccasionally called “temizu.” Temizu also means the ritual washing of hands and mouth that is done in Japan before entering sacred grounds.