If the caulk around your tub is cracked, black, or just plain icky, a tube of caulk and a wet finger can save you from disaster. A well-placed bead of caulk keeps water from seeping behind the tub and damaging the floor and walls.

Step 1: Head to the hardware store to pick up a good-quality tube of caulk made specifically for tub and tile applications. There are many options to choose from, including some that will cure in less than an hour. Silicone-based bathroom caulks often contain mildewcide to help prevent future mold and mildew growth. Silicone sticks well to smooth, slick surfaces, like glass and ceramic tile, but it is somewhat difficult to work with. Latex caulk is easier to apply and works well with porous or uneven surfaces. It is also easier to remove and easier to clean up.

Step 2: Remove the old caulk completely. Use a plastic caulk removal tool, a flat head screw driver and a razor blade to scrape every last bit of caulk out and away. Be careful not to scratch the tub or wall surfaces.

Step 3: Clean the area with bleach water to remove any mildew. Once dry, wipe the surface with denatured alcohol.

Step 4: Apply two parallel strips of blue painter’s tape horizontally, along the shower wall and the tub ledge. Leave a quarter-inch gap between the two tape lines for the caulk to fill.

Step 5: Cut the tip of the caulk tube off at a 45-degree angle. A smaller opening will produce a thinner, more controllable bead of caulk. For caulk gun applications, puncture the seal inside the caulk tube with a long nail or wire.

Step 6: Start at a corner where two walls meet and quickly apply a smooth, steady bead of caulk into the crack. Work fast, doing one wall at a time. Speed is more important than neatness.

Step 7: Dip a finger into a cup of warm water mixed with a few drops of dish soap. Smooth the bead of caulk around the tub, wiping excess caulk onto a paper towel or disposable rag.

Step 8: While the caulk is still wet, remove the painter’s tape by pulling it straight out — not up — from the tub.

— Have a question? Email Linda Cottin at hardware@sunflower.com.