I notice that my bathtub has some yellowing.

Hello. Try using bar keepers friend, and good luck.

If you could borrow or buy a home steam cleaning unit, that would do it.

For my porcelain sink: Wet the sink a little and sprinkle baking soda over entire area. Scrub sink. Then, use hydrogen peroxide and scrub again. Wait 15 minutes and rinse. You can pour the peroxide on the sponge several times instead of using the entire bottle. However, you are cleaning a much larger area so you'll probably use all of it. Do not know what your tub is made of so this formula may or may not work. Good luck.

Easy Off No Fume Oven Cleaner in the BLUE can.

Bar Keeper's friend worked for us!! good luck :)

Pour in a small amount of CLR and let it stay on for awhile. Should remove most of the discoloration without a great deal of scrubbing

Someone just recommended Zud for a sink. They said they got it off line.