Minecraft wiki entry for Block_of_Copper, associated text: In Java Edition, groups of unwaxed copper blocks oxidize far more slowly than single copper blocks that are spaced at least 4 blocks apart. This is because a block in a group being less oxidized than the others slows down the oxidation process for all other blocks within 4 blocks of taxicab distance. However, if one wishes to increase the oxidation speed, placing oxidized copper blocks around less oxidized copper blocks does not offer a speed improvement over simply placing the blocks 4 apart. The calculations for the oxidation behavior are as follows: