Abstract: A separation apparatus (10) for separating a solid or viscous liquid component (28) from a mixture with a readily flowable liquid component (29) of slightly greater specific gravity, for example separating a heavy viscous grease from water. A preferred form of apparatus comprises an upright cylindrical tank (11) including a central cylindrical core (14) and an outer wall between which a separation channel is defined. The channel has a spiral ramp (12) defining its base and is swept by an upright skimmer paddle (24) driven for rotation about the axis of the tank (11). Two apertures are provided in the ramp (12), the first aperture (30) having a trap-door (32) which is normally biassed open and which is closed by impact from a mass of the viscous or solid components (28) as it is swept up the ramp. The liquid component (29) tends to precede the solid or viscous liquid component and so has reached the trap-door (32) before it closes and discharges through this first aperture.