Some good products for cleaning a bathtub are baking soda, cream of tartar, hydrogen peroxide and oven cleaner. These products, along with salt, turpentine, shampoo and vinegar, address the various problem areas in bathtubs.
Baking soda mixed with hydrogen peroxide removes gunk from the enamel of bathtubs. Similarly, cream of tartar mixed with hydrogen peroxide creates a paste that can be applied to stains and removed when dry. Oven cleaner removes rings and stains from white porcelain tubs. Salt mixed with turpentine erases yellow spots that develop on enamel tubs. Shampoo quickly refreshes the appearance of bathtubs by diminishing soap scum. White vinegar can be used to shine porcelain tubs; when left to soak for several hours, it removes stains caused by hard water.