An effective technique for maximizing the explosive charge that a given container can safely handle is to fill the space between the charge and the container walls with a porous medium or a powder. Using the wrong powder, however, can be worse than using no powder at all. Moreover, a powder‐filled container that performs very well with a small charge may also be worse than a powderless system when the charge is increased. An analysis of this problem is developed with the aim of identifying appropriate buffer material properties and the conditions under which breakdown occurs. The results are compared with various experiments performed with graphite powder, coke chunks, granular salt, snow, and vermiculite.