White Vinegar

• White vinegar breaks down the soap scum that causes yellowing in tub enclosures. Fill a large spray bottle with undiluted white vinegar. Spray all the yellowed areas and let it sit for approximately 10 minutes. Scrub down the tub enclosure using a nonabrasive cloth or sponge and then rinse it clean. Repeat with more white vinegar as needed until all the yellow is gone from the tub enclosure.
  
  

Baking Soda

• Baking soda breaks down the cause of the yellowing and makes it easier to remove. Sprinkle the baking soda over the yellowed areas and let it sit for 10 minutes. Scrub the baking soda into the tub enclosure using the rough side of a sponge, or use a stain-erasing sponge. Use more baking soda as needed to get all the yellow off the tub enclosure. Rinse the tub thoroughly before using it again.
  
  

Toothpaste

• Whitening toothpaste works to whiten yellowing caulk or grout. Apply the toothpaste to the yellowed grout or caulk and let it sit for 30 minutes. Use a medium- or hard-bristled toothbrush to scrub the toothpaste into the yellowed areas. The whitening power of the toothpaste should start to work quickly and whiten the caulk or grout within a few minutes. After scrubbing it into all the areas, wipe it off with a damp rag. Make sure all the toothpaste is wiped off, running the shower if necessary to remove it all.
  
  

Hydrogen Peroxide

• If any stubborn yellow stains remain, use hydrogen peroxide to complement the original cleaning method. Pour undiluted 3 percent hydrogen peroxide in a spray bottle, spray the remaining yellowed areas and let the liquid sit for about 30 minutes. Use a sponge or cloth to scrub the stains. Rinse the tub enclosure thoroughly after you have finished scrubbing.