a. a casing to contain a pourable material, the casing having a closed top end and a bottom end with an opening adapted in size to fit closely over the rim of the receiving vessel onto which the pourable material is to be delivered;

b. an encloser covering and sealing the opening at the bottom of the casing when the encloser is in a normally-closed position, the encloser having a top surface, a bottom surface shaped so as to lie flat atop the rim of the receiving vessel, and a peripheral sealing edge that sits in contact with the casing, preventing escape of the pourable material from the casing;

c. a closing spring, located inside the casing and extending from the closed top end of the casing to the top surface of the encloser, the closing spring being compressed to apply a downward force to hold the encloser in the normally-closed position, the closing spring being further compressed by pressing the bottom surface of the encloser downward against the rim of the receiving vessel, to open an annular space for flow of the pourable material from the casing onto the rim of the receiving vessel, and to block flow of the pourable material into the interior of the receiving vessel; and,

d. on the bottom surface of the encloser, a blocking plug, tapered from a diameter approximately equal to an inside diameter of a lip of the receiving vessel at the plug's point of joining to the encloser, to a slightly smaller diameter at the plug's bottom, whereby, when the plug is inserted into the receiving vessel and the encloser pressed down against the vessel's lip to dispense the material, the dispenser is centered above the receiving vessel, and the path to the interior of the receiving vessel is further sealed off against flow of the material.