How to Caulk a Bathtub Like a Pro

A clean bead of tub caulk separates a bathroom that looks renovated from one that looks dated. The trick is prep, not technique.

Most failed tub caulk fails because the old caulk wasn't fully removed or the joint wasn't dry. Pull every scrap of the old bead out with a plastic caulk-removal tool and a razor blade — if you can see a thin film of silicone residue, the new bead won't bond. Wipe the joint with isopropyl alcohol and let it flash off for 10 minutes.

Fill the tub with water before caulking. The weight pulls the tub down to its loaded position — caulk a dry tub and the joint will crack the first time someone takes a bath.

Use 100% silicone (not latex/silicone hybrid) for wet areas. Cut the tip at 45° with an opening matched to the joint width — about 3/16" for most tubs. Lay a continuous bead, then tool it once with a wet finger or a $3 caulk-finishing tool. One pass only; going back makes a mess.

Let it cure 24 hours before draining the tub. Cutting that short is why caulk peels away from the wall a month later.