The focus of this paper is on the flotation microprocess of attachment by sliding, considered to be an important microprocess in Rotation separation. A detailed discussion is provided as to which forces are important for this microprocess during Rotation deinking, By including the resistive force due to film drainage, the gravitational force, and the flow force between the bubble and particle, and accounting for both Stokes and non-Stokes flow conditions, a closed-form approximation for the probability of attachment by sliding (P-asl) has been developed. The expression presented here is a function of fluid properties, bubble and particle physical properties, and the ratio of the initial-to-critical film thickness separating the bubble and particle (h(0)/h(crit)). Using this result, it is shown that P-asl generally decreases with increasing h(0)/h(crit) and increases with increasing bubble and particle radii and particle density. However, local minima are observed. Additionally, the transition from Stokes to non-Stokes flow conditions results in an abrupt transition in the P-asl predictions.