Difference between hold chamber and cold chamber pressure

What is the difference between hot chamber and cold chamber process ?

The plunger and cylinder are permanently submerged in the molten metal in the holding furnace in the hot-chamber die casting process, whereas a cold chamber machine the metal is ladled after each shot cycle, either manually or automatically, into the injection cylinder. So the contact between the molten metal and the machine parts (cylinder and plunger) is limited only for a short period of time.