Abstract: A dump bailer is lowered on a wireline in a well through tubing for placing a cement slurry on a retainer located in the well. The dump bailer has a weight bar assembly that includes upper and lower sections that are extensible relative to each other. The upper weight bar section has an electrical contact that engages the electrical contact mounted in the upper end of the housing of the dump bailer. The lower section has a seal which separates the housing into upper and lower chambers. Cement is pumped in from the bottom, pushing the weight bar assembly upward until the contact on the upper weight bar section engages the upper contact. A detonator is located on the bottom of the lower weight bar section. Explosive force of the detonator transmits a shock wave through the cement slurry to expel a shear plug located on the bottom of the housing. The weight bar assembly pushes the cement from the slurry once this occurs.