There are two type of copper bathtub and bathroom sink finishes offered by Rustica House brand. The tub or sink is made of hammered copper with pre-selected patina color or made of natural metal without any treatment. The first version that is the most common and accounts for 95% of sales is covered with transparent lacquer preventing further natural patina creation. You can only clean it with sponge and the color is permanent. The second type will get darker quite quickly. You can leave it as it is or periodically clean patina from the bathtub surface to its original state. Use simply water with soap solution while gently scrabbling with scotch pad. Don’t over do it so there are no scratches on the copper tub left after patina removal.