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20 mule team borax! best bathtub cleaning method (just make sure to rinse REALLY good afterwards, before anybody uses the tub).
Use 20 Mule Team Borax to clean tub, and other cleaning tips
Natural bathtub cleaner using just borax. Didn't work for me in the past, but may try again.
Clean bathtub - 20 Mule Team Borax and stiff brush (better than bleaching)
How to clean a bath tub or shower that look like this - 20 Mule Team Borax. Wow.