it has to do with how many dissolved solids are in water
Tds=ts-tss
Drain and refill all or a portion of the total volume of water.
Sterling silver is copper dissolved in silver, steel is carbon dissolved in iron, bronze is copper dissolved in tin.
copper and tin make bronze copper and zinc make brass iron and nickle make stainless steel iron and carbon make carbide steel iron, tungsten and carbon make tungsten carbide.
a solid a solid