An isostatic test system useful for the isostatic testing of frangible structures, such as honeycomb ceramic monolith structures useful as catalyst supports, is provided by a combination of elements including means for providing a pressurized fluid, a rigid container, a pressure-expansible fluid impermeable means for receiving the pressurized fluid and adapted for insertion within said container to encompass or surround the structure for isostatic testing therein, fluid pressure measuring means communicating with said pressure-expansible fluid impermeable means for measuring fluid pressure therein and means communicating said means for providing pressurized fluid with said pressure-expansible fluid impermeable means for pressuring said pressure-expansible fluid impermeable means.
