Should the lid be a tight fit or loose
Most crock pots are made of porous ceramic and is relatively brittle. It is glazed on all sides (except the bottom usually), to make it hold liquids without absorption. The lids, usually glass or thermoplastic, sit of top, but do not usually fit tightly as this could crack the crock. Also, it is not a pressure cooker, so you want excess steam to vent. The lid just keeps the heat inside and allows condensation to drip back into the crock, reducing the speed at which the fluids cook off, thus the term slow cooker.
