A smectic-A free-standing film is always connected by a meniscus to the frame on which it has been stretched. The meniscus acts as a dissipative reservoir and is characterized by its permeability. We propose a method to measure directly this quantity by equilibrating two menisci in correspondence with the same free-standing film. The permeability is shown to depend on the film thickness, in full agreement with previous indirect measurements obtained by analyzing the growth dynamics of dislocation loops. An improved model of the meniscus is proposed to interpret all the data.