One of my original ideas involved a pattern growing up the side of a cup and water vessel. To do this thermochromic inks would have to be used. Standard inks respond at 15C 20C 31C and 47C. You can get special engineered inks and they can be made to respond at temperatures between -10C to 69C, not high enough for brewing good tea. This idea might not work they way I want to but the idea of waiting for something to complete is nice, it forces you to slow down and enjoy the poetic growth of the pattern leading to great tea.