Abstract: Devices and methods for reliably and reusably creating an airtight seal on a tapered nozzle attached to a container of air-curable material. The device is a unitary expandable tube with an open end and a closed end filled with putty-like material. In one embodiment the device is placed over the nozzle, the device and nozzle are pushed together until the open end of the device flares around the outside diameter of the nozzle, and the nozzle tip displaces some the putty-like material thereby expanding the closed end of the tube to accommodate the displaced material.