In principle, liquid layers between bubbles can be stabilized by a coating of fine solid particles even in the absence of surface-active agents in the liquid. Theoretical modeling of a two-dimensional liquid layer between bubbles containing one row of solid particles suggests that in three dimensions such a layer would be unstable unless the solids all touch. This hints at a possible mechanism for bubble stabilization and subsequent rupture in the waste stored in underground tanks at the Hanford nuclear reservation.