Plots of the radial profile of the H⁺ fraction at t = t_rec for A1 (first three plots) and A3 (last three plots). Results for n_H = 10   cm^-3 are shown (results for higher densities were indistinguishable) for A1 with cell optical depths Δτ₀ ≃ 1 (top left), Δτ₀ ≃ 10 (top right), and Δτ₀ ≃ 30 (centre left), and the equivalent plots for A3 are centre right, bottom left, and bottom right. For A1 and A3 the criteria dt06-dt11 all provide good fits, very close to the dt12 results. As in previous figures, the discreteness of the grid is seen in the Δτ₀ ≃ 30 plots.