Antibubbles: evidences of a critical pressure

We present experimental investigations of antibubbles. Such an unusual fluid object is a thin spherical air shell surrounding a liquid globule. We explain how to produce them and we study their stability. By overweighting antibubbles with a small amount of salt, they sink and pop at a definite depth. A critical depth related to a critical pressure has been found. A modified Laplace law describes the air shell thickness evolution with respect to pressure. This law combined with surfactant layers interaction allows to explain the critical depth for antibubble stability.