For the bathtub, you'll need caulk designated for the bathroom or one classified as ideal for the kitchen, most likely silicone or acrylic latex. Although silicone doesn't need to be replaced as often, it is difficult to smooth and picky about what it adheres to.

You should scrub and rinse the part of the tub where the tub deck meets the tile to avoid grime and residue while caulking. You can also wipe the area with bleach or vinegar after removing the old caulk, but allow the seam to dry completely before applying the new caulk.

Use a damp cloth and baking soda to rub off the residue left by the old caulk, or for stubborn residue, scrub with rubbing alcohol. Make sure to have adequate air circulation in the room, and then wipe off the baking soda and allow the area to dry completely.

To effectively remove the old caulking, use a scraper with a razor blade, but watch the angle of the blade to avoid scraping your tub. If you are less comfortable with sharper instruments, you can use a blunter tool, but it might prolong the length of the project.

It’s essential to remove the old caulk to ensure that the new caulk seals properly. Use a razor-cutting tool such as a box cutter or putty knife to start slicing into the seam area between the tub and tile, making one continuous slice to remove it easily.