Using an image made of thin and thick dots produced on an alkaline-sized paper by a photocopier and a laser printer, respectively, flotation kinetics of toner particles were measured in repulped papers. Flotation data could be fitted to a modified first order relationship, with the fraction of unfloatable particles in the stocks being used as an adjustable parameter. Rate constants for smaller particles (<100 mu m) were slightly larger for toner particles from photocopier-printed paper than from laser-printed paper, The largest differences between the two types of loner particles lay in the fraction of large, unfloatable particles, often rich in fibres embedded in the toner layer, This variability in the number of unloatable particles was explained by the thickness and areal density of the print, by its degree of adhesion to paper, and by the froth stability. Although fibre-containing toner specks float at a lower rate than fibre-free ones, the addition of a calcium soap collector increased their rate of flotation. The key role of froth stability on flotation kinetics was also demonstrated. Losses of fibre and filler in the froth were shown to be caused solely by entrainment in the interbubble water.
