Diffusion in liquid is relatively consistent. When paper is soaked and allowed to dry, it can produce uneven concentrations as regions evaporate at different rates, and solutes move along with the flow of solvent. A good example of this is water color painting: if you mix paint into water and then apply it to the paper, the resulting patterns may be less uniform than when applied.
I see, thanks. I guess drying is essentially crystal regrowth, and the thing about growing crystals is that the material concentrates around the nucleation sites and spoils the nice even distribution that you get from being in solution.
Seems like one can expect a hit to be a more precise dose than a half-hit, presuming it's still done that way.
