A cap is provided for a laboratory vessel. The cap includes a lid that can be rotated relative to the laboratory vessel from a closed position to an open position. The lid includes at least one tab dimensioned and disposed for receiving manual digital pressure for opening and/or closing the lid. The tab is in an offset position to prevent a thumb or forefinger from passing over and in contact with the opening to the vessel. Additionally, the lid includes a shield inwardly from the tab for further preventing contact between a finger and the open top of the vessel.