Testers began with ordinary tiles covered with soap scum. Then they used a special soap-scum solution to spray the tiles daily for 14 days. They let it dry in between sprayings until there was a thick layer of soap-scum buildup.
Testers also created their own rust to put on another set of tiles. Finally, a third set of tiles was covered with mildew.
Consumer Reports pitted each cleaner against the dirty tiles. Neither Scrubbing Bubbles, or any of the other aerosol foam cleaners, did a good job at removing the built-up grime.
And there was another problem.
"The aerosols say you don't have to rinse," said Pat Slaven from Consumer Reports. "You can see there's still residue left on the tile."
What did get the job done were powered cleansers. Comet Scratch Free Disinfectant Cleanser with Bleach and Ajax with Bleach Scratch Free Cleanser earned top ratings and cost around $1.
As for the so-called green cleaners, most of them were only so-so. But one was a clear winner -- Clorox Green Works Natural Bathroom Cleaner, which retails for $3.50. It rated higher than nearly all of the spray cleaners and costs less.