is environmentally positive, you may ask? If you grew the bamboo or cedar in your backyard and then made it yourself, the answer is – definitely! These examples might not be the greenest and they cost a pretty penny, but it must feel wonderful to bath in wood. Wood holds the heat longer than other tub material. Unfinished wood tubs must be used regularly or kept partially filled with a bit of water to prevent them from drying out and warping or shrinking. In the past bathtubs were made of wood, marble or ceramic tile. Cast-iron tubs came into fashion starting in the 1880s, then enamel over steel, now mostly formed acrylic, fiber glass or porcelain on steel.