Structure of the envelope of our representative evolving 0.6 M_⊙ DA white dwarf. The ordinate gives the fractional mass depth in logarithmic units. The small dots define “isocontours” of opacity, and some are labelled by their value of log κ. The small filled circles indicate the boundaries of the superficial convection zone. The vertical dashed lines indicate the blue and red edges obtained with our TDC treatment with ML2/α = 1.0.