(57) The use of insoluble particulate bentonite for thickening or increasing the viscosity of emulsion explosives is described. The bentonite (swellable clay, montmorillonite) is dispersed throughout the emulsion, without dissolving in either phase and without causing crystallisation, by admixture of the powder with the prepared emulsion in a low shear blender. The resulting emulsions have increased viscosity and rigidity which provide higher gas bubble retention and hence longer shelf life.