2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/128673We find that a column of glass beads exhibits a well-defined transition between two phases that differ in their resistance to shear. Pulses of fluidization are used to prepare static states with well-defined particle volume fractions $ϕ$ in the range 0.57-0.63. The resistance to shear is determined by slowly inserting a rod into the column of beads. The transition occurs at $ϕ=0.60$ for a range of speeds of the rod.4 pages, 4 figures. The paper is significantly extended, including new dataSoft Condensed Mattertext