An adjustable seal that is kinematically linked to a container to provide a complete seal of the container opening and to allow easy access to contents therein. The seal includes a lid portion and a sealing means, as well as a lever and a yoke, which are kinematically linked together via a plurality of pivot points. The seal also comprises a spring system having a springfront, a spring rear, and a spring, and the spring system is likewise mechanically connected to the other components. Due to this kinematic linkage, the closure is moveable among different positions to provide various degrees of access to and from the container via the container opening. As a result, the sealing system of the present invention protects against spillage and splash by completely sealing the container opening, as well as provides easy access to the contents of the container.