summaryIn this study the damping of ultrasonic waves as well as the compressive strength of amalgam has been measured as a function of the time delay between trituration and condensation.The damping of the ultrasound energy is proportional to the macroporosity, which is caused by lack of plasticity and difficulties encountered in combining various amalgam portions. Also, damping is increased with the condensation delay. Nearly all brands investigated showed a decrease in strength and an increasing macroporosity with delay in condensation.The results indicate that the macroporosity caused by condensation delay determines primarily the mechanical properties of the amalgam restoration.