Evolution with the surface luminosity L of selected physical and chemical quantities across WD models with masses equal to 0.55 and 1 M_⊙. The vertical axis displays the logarithm of the mass m_r enclosed between the surface and a point at a distance r from the centre, normalised to the total WD mass M_WD. Dashed lines mark the boundaries of the carbon-oxygen core as well as the helium and the hydrogen envelope. The lower boundary of surface convection is denoted by dotted lines. The solid lines show the position of the mass layers where θ = 1 and 0.1.