Method comprising: supplying electricity to at least one wave transducer (25) for synthesising an ultrasonic surface wave propagating in a medium (10) to a body (15) arranged on one side of the medium, at least one portion of the electrical supply energy being converted into heat by the transducer, the electrical energy supplied to the transducer being sufficient for the heat and the energy of the ultrasonic surface wave to cause: —the body to melt when the body is in the solid state, and/or—the body to be maintained in the liquid state when the temperature of the medium is below the solidification temperature of the body.