Doesn't work on silicone caulk - old or fresh :-(
I was quite disappointed to find that this did not work hardly at all on silicone caulk in the shower, even when left on for 2+ hours.  It also did not clean up fresh silicone, even think layer smears.  Also, be aware that the spray mechanism easily causes splash-back of the acetone-based product and it can splash into your eye.  Wear eye protection!  It would be better if it were a brush applicator for more targeted, less-splashing application.
Rating: 1 stars