Cleaning a set-in mildew stain on fiberglass shower
I'm new here, and have found the forums to be very helpful for tackling tricky household cleaning problems. I have browsed through the many posts here, but I haven't found anything to tackle my latest issue, so I hope you all can help.
I am trying to get rid of a very stubborn mildew stain that has built up over time in the fiberglass shower we have in the master bath of our house. This master bath rarely gets used, as I'm caring for this house while my parents are away overseas, and have always used the main bathroom. I went to check the master bath and saw that not only do I have a leaky shower to contend with, some terrible mildew has built up on the shower floor over several months. I've been able to get rid of most of the stain, but some of it still remains.
I've tried most of the products and methods recommended here so far. Tilex and Lysol spray-on bathroom cleaners, Lime Away, Mr. Clean Magic Erasers, Barkeeper's Friend (the abrasive and soft-scrub varieties), and finally Oxi-Clean powder directly onto the stain itself. I've tried the last two methods three or four times, including leaving the Oxiclean on overnight to see if it would improve the appearance of the stain.
I've had the most success with the Barkeeper's Friend and the Oxiclean, but I am really hoping to remove the stain entirely. Is there anything else I should try? Should I continue with the Barkeeper's Friend and Oxiclean over several days to see if it will continue to remove the stain, or just settle with the results as they are? Any other tips or advice I would gladly welcome. Thanks in advance for the help!
I've included a photo for reference. I apologize that the detail is not quite as sharp, but you can still make out the outline of the stain.