Abstract: A sealing mechanism for use with open top hoppers when being field by gravity loading. The sealing mechanism has been specifically designed for the plastic industry which dumps the pellets of plastics and pigment from a mixer into an open top hopper. One embodiment is a sleeve that fits over the spout of the mixer and over the open top of the hopper. The sleeve is cut so it will fit over the spout and is sealed by a piece of tape. The bottom end of the sleeve is cut so that it will fit over the hopper and by its tensile property will fit snugly so no pigment will be lost when the mixer dumps the pigment in plastic into the hopper through the sleeve. Another embodiment is a liner that is designed to fit within a hopper with an open bottom. The liner is specifically designed so it will fit over the spout of the mixer and is sealed tightly so no pigment will be lost in the dumping process by a piece of tape.