Containment systems and methods safely and permanently encapsulate a sharp portion of a sharp medical instrument (e.g. a hypodermic needle). The containment system includes a cap or other container formed of a durable and flexible material having a rim defining an open end configured to receive a sharp portion therein, an interior surface, wherein at least a portion of the interior surface comprises a puncturing element, and a bladder contained within the cap proximate the puncturing element, the bladder containing a first component of a liquid hardenable solution. Opposing sides of the cap can be deformed under external pressure to cause the puncturing element to puncture the bladder so as to release the first component of the liquid hardenable solution from the bladder such that the first component contacts the sharp portion and the sharp portion is substantially permanently retained inside the cap by the liquid hardenable solution.
