Most modern bathtubs are made of acrylic or glass fibers, but some are made of porcelain-coated steel or wood. Old-fashioned bathtub in the western world are usually made of galvanized steel or iron (cast iron) are coated porcelain.
Until recently most bathtubs made in the form of more or less rectangular, but with the advent of the formation of acrylic techniques, the variations were more diverse way. The tub is usually white, but now other colors were commonly found.
