zavarka и kipyatok

[kobak]

Observe that the color of the tea does not change if you look from above, assuming the water is completely transparent (the proof of this statement is left as an exercise to the reader). Therefore, all you have to do is pour zavarka until it reaches the desired color, and water it down thereafter. Cups with increasing horizontal cross-sections do not offer such an easy method, you will either have to solve an integral equation or make an educated guess.

Отличный текст про zavarka, kipyatok и podstakannik: russain tea HOWTO.

(спасибо dimrub).