The penetration behaviour of impacting particles into glycerol solutions has been studied. A high-speed video technique has been used to observe the particle motion during penetration and to measure the transient displacement of the particle. The experimental range is 10 less than or equal to Re-0 less than or equal to 61 000, 410 less than or equal to Fr-0 less than or equal to 70 000 and 0.287 less than or equal to rho’ less than or equal to 0.953, where Re-0, Fr-0 and rho’ are the particle Reynolds number (nu(0)d(p) rho/mu), the particle Froude number (nu(0)(2)/d(p)g) and the solid to liquid density ratio (rho(p)/rho) respectively. Comparing a solution of an equation of motion for a particle penetrating a liquid interface with the corresponding experimental results revealed that the standard drag coefficients are inappropriate to represent particle impacts owing to the dynamic nature of the flow, This effect was more pronounced with increasing rho’, The critical condition for particle penetration is Re-0 approximate to 250.