A method of removing extraneous matter from a mixture of extraneous matter and waste glass, said extraneous matter having a greater specific surface area and greater resistance to the water flow per unit weight than said waste glass comprising providing an inclined drum having an upper end, a lower end, an inner peripheral surface and a helical wall on said inner peripheral surface, said helical wall being inclined towards the lower end of the drum, introducing water to the drum at said upper end to provide a flow of water running in a substantially axial direction down the interior of the drum over said helical wall, said wall having a depth and pitch to produce a water flow zone substantially reaching said inner peripheral surface, feeding waste glass mixed with extraneous matter into the drum to drop into said flow of water, rotating the drum at a speed to bring the waste glass into a dispensible suspension-resembling state in the water flow with a rocking motion imparted to the glass circumferentially of the drum to cause the waste glass in said suspension-resembling state to be moved toward said upper end of the drum by said helical wall and the extraneous matter to be moved toward said lower end of the drum in said flow of water whilst periodically causing the waste glass and extraneous matter to encounter disruptions in their movements, and discharging the waste glass from the upper end of the drum and the separated extraneous matter from the lower end of the drum.