Porcelain bathtubs are the most popular kind of bathtub used in the United States. They are affordable, low maintenance and have more durability than acrylic bath tubs. The base of a porcelain tub can be made of glass, tile or steel then coated with porcelain enamel and heated at very high temperatures. This process creates a smooth, durable surface for the floor of the tub. It is a very smooth hard surface that is moisture resistant