release the pressure on the grease gun,,they vary on brand etc,,as some have a small trigger by the plunger rod,,or others have a little ball on the top push this will release air when loading ,,,others pull plunger back and lock ,unscrew top carefully to release pressure then screw back on,,,all grease bleeds,hang gun up bottom down orwrap in a old large rag,,refrigeration helps the effect of storage, found some synthic greases (Mobil) bleed and seperate badly,,,Al. complex ,calcium better,,,,,,,BL