I've done some research, and I've looked at the derivation of the diffusion equation, but I don't want to reproduce even a more simple version of it. I'd like something that can I do almost exclusively myself. The point of this is not to plot some graphs, and extract some line of best fit or exponential equation, but to work toward a model (tea concentration as a function of time, probably) that can fits data, with improvements being made accordingly. I've tried the Rayleigh method of dimensional analysis as a start, but with few variables, I couldn't see it though. So, are there any mathematical techniques/methods that you guys suggest I could use, or anything else? I'm not looking at something exact, but maybe an approximation for a cylinder, or sphere, maybe. Thanks so much.