Minecraft wiki entry for Nether_survival, associated text: If you can find and reach a lava flow's source block, you can bucket it just like in the Overworld. Unfortunately, in the Nether, much of the lava is pouring down from great heights. Normally, use cobblestone, or iron bars to contain lava or direct it away from you (if you use flimsy blocks like dirt or netherrack, a ghast fireball can undo your work in a moment!) As always, if you mine upward, then watch for dripping red particles (if you have particles turned on). The drip itself does no damage, but if you mine a dripping block, lava pours down. If you wish to get rid of lava flowing from the ceiling (in your way, or immediate hazard), you must block jump up to the source (or simply aim at the ceiling), and cover the hole with any non-flammable block (if it's flowing straight down from a flat ceiling, you may need an extra block next to the flow to place the dam). One must be extremely careful about the placement of the block, however—if misplaced, the block can just spread the lava wider.