I “pinned” this awhile back and it’s been in the back of my head to give it a try!  I finally remembered to add it to my grocery list and I tried it out over the weekend.  My kitchen sink is porcelain and has yellowed a bit around the drain and Comet just wasn’t taking it away.  I’ve sprinkled Comet in the sink and let it set overnight and it still didn’t go away.  This stuff – cleaned it like crazy and the weird thing is it seems like my sink stays cleaner!!!  This cleanser is great and if you have ANY porcelain sinks or your tub, I would totally try this!!!! I’m giving it 5 stars!!!!

http://www.classyclutter.net/2013/04/my-secret-weapon-for-cleaning-your-sink-toilet-and-bathtub-spring-cleaning-day-3.html