Experiments on self-similar Rayleigh–Taylor instability-induced mixing in gases in the Earth's gravity conducted on the OSA facility at the Russian Federal Nuclear Center–VNIITF are described. These experiments are distinguished from other experiments, usually performed with immiscible liquids in a tank or with miscible liquids initially separated by a solid barrier that is retracted, in that a membrane (of ∼1 μm thickness) with liquid soap film embedded in a thin wire array (with microconductors of diameter 20 μm and with a spacing of 4 mm) initially separates the fluids. An electric current to initiate the fluid interpenetration and mixing destroys the membrane. Experiments performed for three different Atwood numbers are described: in SF6-Ar with A = 0.54, in SF6-He with A = 0.94, and in Kr-Ar with A = 0.35. Various parameters of the mixing were measured from Schlieren photographs. In particular, the dimensionless rate of mixing front growth is α = 0.078.