Abstract: Disclosed herein is a hair treatment sink assembly and a method of collecting hair treatment materials during treatment operations. Further disclosed is a drip collection tray for collecting hair treatment materials during a hair treatment operation. The sink assembly is comprised of a basin with a drip tray installed beneath it to collect any hair treatment materials falling outside the basin. The method of collecting hair treatment materials during a hair treatment operation comprises the steps of resting a patron's head over a basin, applying hair treatment materials to the patron's head and catching the materials falling from the head in the basin and the materials falling outside the basin in a drip tray installed below the upper rim of the basin. The drip collection tray is comprised of a pan with surrounding side walls and a drain. The pan has portions that extend outside the envelope of the basin, when viewed in plan, on at least two side portions and the front portion of the basin.