Baars et al. pointed out that the decrease in depolarization ratio of smoke in the stratosphere with time is consistent with the aging of smoke particles and the addition of a coating around the solid black carbon core aggregates, which would change the shape towards a spherical form. We add here that the coating would also need to be in a non-glassy and lower viscosity state, which may be accomplished by the uptake of H2SO4 present in the stratosphere, as shown above.