The caulking on my tub surround has turned black. I have tried all kinds of mildew cleaners, but nothing works. I hope you have a suggestion!

Mildew can be difficult to remove from silicone caulking because it grows into the caulking. I suggest removing the caulking with a putty knife and replacing it with new caulk. If replacement is out of the question, you may want to try applying Soft-Scrub with bleach. Squirt the soft scrub on the the caulking and let it sit several hours. Rinse throughly. On heavy mildew it may be necessary to let the Soft scrub sit overnight.