  We propose an explanation for the commonly-seen fading in the density of a
stain remaining after a droplet has dried on a surface. The density decreases
as a power $p$ of the distance from the edge. For thin, dilute drops of general
shape this power is determined by a flow stagnation point in the distant
interior of the drop. The power $p$ depends on the local evaporation rate J(0)
at the stagnation point and the liquid depth $h(0)$ there: $p = 1 - 2
(h(0)/\bar h)(\bar J/J(0))$, where $\bar h$ and $\bar J$ are averages over the
drop surface.
