DH and I are at the point of needing to replace the caulking in our shower. The old stuff is pretty well mildewed to pieces, and there are definite signs of leakage.
I’ve found lots of information online about re-caulking, but nothing that gives any useful information about removing the old caulking first. (“Step 1: Remove old caulk. Step 2: Load the caulking gun”…)
While I’m sure that some of the old caulking can simply be pulled away, I’m guessing that there are tricks that can make this much easier, as well as more efficient. We truly do want to remove all of the old caulking before applying the new stuff.
Really old linseed based caulking can be damn near impossible to remove. Same goes with modern silicone based stuff.
The most common latex/siliconized ones can be pulled off with just your hands for the most part, especially if the surface wasn’t properly prepared.
Your best course of action is to go at it at first with an old wood chisel (or at least one you never plan on using on wood again). Gouge and scrape out as much as you can without scratching the enamal or the tile. (be doubly carefull around fiberglass).
Second stage is to clean up as best you can with a paint scraper and single edge razor blades.
Then scrub the area thouroughly with steel wool or a “green scrubbie” pad and cleanser.
Rinse the area with clear water and a clean rag until it is totally clear of soap and caulk residue.
I usually follow with a good wipe down with laquer thinner to insure a clean surface for the caulk to adhere to.
Surface prep is key to a no-leaking seal a bad caulk job can fail in just a few months and cause many, many dollars in damage.
Be sure and practise a few feet of test bead before you jump into the tub. A sloppy job is a pain to clean up and needs to be started over.
Oh and be sure and pick up a good quality of tub and tile caulk. I would avoid pure silicone as it can be difficult to handle.
I would recomend Alex II w/ Silicone for its ease of handling but I’m sure many of the pro’s around here would scoff at me and call it “painters” caulk.
I recently did this, removing old silicone sealant. It actually turned out to be fairly easy, if a little tedious - I used a Stanley knife (which I think is known as a “boxcutter” in the US) to cut it out, and then to gently scrape away the residue. For tricky corners, I used a razor blade. Then I sprayed it all with limescale remover to dissolve the little ridge of scale deposits that had formed along the edge of the sealant, which came off quite easily with a scouring sponge. Then rinse well, allow to dry and you’re ready to go.
Check your hardware, paint or building supply store. There are removers available for latex caulk and other types of caulk from well-known companies like DAP and 3-M. They don’t dissolve the caulk, but they soften it and make it easier to peel off. Check an inconspicuous area of your tub to make sure it isn’t affected by the caulk remover before applying it wholesale.
I’ve also used a hand held grout remover tool, not the dremel kind. The one I bought has toothed end available that grabs the grout and rips it out. Follow up with a razor blade, a blade holder helps a lot here, and the other steps already mentioned.