Palmer uses flashing which is an efficient drilling method in that water or some other thicker liquid, such as a mixture of water and clay, is driven into the borehole through the rod and bit. The water rises along the rod on its outer side, between the walls of the borehole and the rod, with such a velocity that the broken rock fragments are carried up by this water current (direct flushing). Alternatively, water enters the borehole around the rod and issues upwards through the rod (indirect flushing).