Luminescence from laser-induced bubbles in water-glycerol mixtures: effect of viscosity. 
The luminescence pulses emitted from collapsing laser-induced bubbles in water-glycerol mixtures are studied as a function of the mixture concentration and applied hydrostatic pressure.  The primary effect of increasing the glycerol concentration is to increase the viscosity of the fluid.  The pulse duration of the luminescence is found to increase by more than a factor of two as the concentration increases up to 33% glycerol by volume, where the viscosity is nearly four times that of pure water.  At higher glycerol concentrations the pulse duration remains nearly unchanged, until no luminescence can be observed at concentrations above 60%, corresponding to a viscosity greater than 15 times that of water.  The pulse duration further increases with applied pressures up to 8 bar, similar to that observed earlier in pure water.