My idea is to package a plastic tool that can be used to scrape unpleasant black mold around tub area or sink. The plastic tool on the other end would have a shape to make new caulking groove. This tool would be packaged with CLOROX Clean-UP with bleach & a small durable plastic brush.A brush strong enough to get rid of small fragments of bad caulking. A instruction sheet with hints on avoiding black mold and applying fresh caulking. I would say to make sure area is cleaned with CLOROX CLEAN-Up before applying fresh caulking, make sure area is dry,suggest using hair dryer to dry area.I would also propose to say not to use area for several hours to allow fresh cauking to dry throughly.