scaled density, $g = \rho/\rho_s$ stands for all the non-cloud gas in the model. Thus we compare the intercloud gas in a simulation with $$M_x = \int_0^{r_s} 4 \pi r^2 \rho\,dr = 4\pi r_s^3 \rho_s \int_0^1 g(x)
    x^2 \,dx,$$ (from WL) where $g \equiv \rho/\rho_s$ is derived by integrating the set of equations in WL for given values of $\tau$ and $C$. To find the value of $\tau$ corresponding to a particular time for a simulated remnant we use the actual value for $C$, calculated as the initial ratio of mass in clouds to that in the intercloud medium within the shock volume. We then do a search, using a root finding method, wherein we calculate the values of $M_x$ given values of $\tau$ until we match the value for the simulated remnant. This is the method used to produce Figure \[fig:tevap\].

![Evaporation timescale factor, $\tau$, of WL vs. remnant age. In the WL model $\tau$ is a constant, but here we see that it varies considerably over the age of our simulated remnants. The 3D runs show smoother behavior because more clouds are sampled at any given age. Here $\tau$ is calculated using the density criterion for deciding whether 