coffee rings
The coffee-ring pattern originates from the capillary flow induced by the differential evaporation rates across the drop: liquid evaporating from the edge is replenished by liquid from the interior. . . The resulting edgeward flow can carry nearly all the dispersed material to the edge. As a function of time, this process exhibit a "rush-hour" effect, that is, a rapid acceleration of the edgeward flow at the final stage of the drying process. . .
coffee rings
The coffee-ring pattern originates from the capillary flow induced by the differential evaporation rates across the drop: liquid evaporating from the edge is replenished by liquid from the interior. . . The resulting edgeward flow can carry nearly all the dispersed material to the edge. As a function of time, this process exhibit a "rush-hour" effect, that is, a rapid acceleration of the edgeward flow at the final stage of the drying process. . .