Minecraft wiki entry for Things_not_to_do, associated text: By conserving materials in their original forms, the player can save several slots of inventory and chest space. The player may also need to recollect the original item if they need more of it later. There are exceptions, such as how a player can "compress" 9 ingots into a single block and change the block straight back into 9 ingots. Note that nether wart blocks, packed ice, blue ice, partly or fully oxidized (before oxidation is removed) or cut copper blocks, and blocks of amethyst cannot be crafted back into their respective components.