Minecraft wiki entry for Defeating_a_Nether_fortress, associated text: If the components are quickly accessible, Fire Resistance potions should be the first you brew. Lengthen then by brewing redstone into the Fire Resistance potions. To keep brewing potions past awkward, you'll want to put all three potions back in their slots if you took them out, and then put the magma cream in and then the redstone after that finished. Voila, you have 24 minutes of Fire Resistance.