This paper examines the detachment of coarse particles from oscillating bubbles as a function of particle hydrophobicity and shape, as well as medium viscosity. The detachment experiments were conducted using a novel electro-acoustic technique for both ground quartz particles and spherical glass beads of various diameters and hydrophobicity. The detachment force for both types of particles, calculated from the maximum vibration amplitude at which a particle detaches from a bubble, increased with an increase in the contact angle of particles and viscosity of the suspending medium. At low vibration frequencies, the quasi-static model predicts the experimental detachment force reasonably well. In contrast, at high vibration frequency and, particularly, in high viscosity medium, the quasi-static model does not predict the experimental detachment force. It is hypothesised that the magnitude of the detachment force is determined by the dynamic contact angle, which is governed by the velocity of movement of the three phase contact line. Larger detachment forces were observed for the quartz particles compared to that of the spherical glass beads of the same size range and similar contact angle value. The stability of the bubble-particle aggregates at high viscosity has been related to the dynamic contact angle of particles. At high viscosity, the rate of movement of the three phase contact line, which governs the dynamic contact angle, is reduced thus resulting in more stable bubble-particle aggregates. (C) 2011 Elsevier B.V. All rights reserved.