Perhaps you'll remember how the main bathtub looked when we bought the house. It needed, umm...some elbow grease. A few days after we settled in I went to tackle it and realized the sad truth. The previous owners left it that way because it couldn't be scrubbed away. It was embedded in the silicone caulk. Yuck. It gave me the heebie-jeebies just showering in there. A call to my ever-handy, highly-experienced father yielded the verdict of death to the silicone. Rip it/scrape it out. Scrub, scrub scrub. Tape for protection. And then, re-caulk with quick-drying, flexible kitchen and bath silicone (in a tube). I was pleased with the results of a few hours of work.
Except that, in the process, I had to reattach/caulk a few bathtub tiles and when I scraped the first tile, the one below it fell right off, taking the supporting plaster right with it. So, in the last picture you can see the gap left behind. Stay tuned to see the results of that project.