In real life, both copper and bronze will slowly "oxidize" when exposed to oxygen. This process is sped up by other substances, among them is water.
So, with this mod, when copper or bronze touches water it will slowly turn into "Oxidized Block".
You can also craft "Oxidized Block" by mixing copper or bronze block with a water bucket.
Interesting and cool mod concept, however the textures don't really fit with Minetest game.
Other than that cool mod.
simple amd good mod nothing more and nothing less