When you make koicha (thick tea), be sure to use fairly hot water, dry the tea bowl before starting to make it, and stir the tea powder well into a paste; but it shouldn't be stirred so that the tea has bubbles or lumps.' (Doka by Rikyu)
「濃茶には湯加減あつく服は尚ほ泡なきやうにかたまりもなく」(利休道歌)