Homework: How to caulk a tub
The contact point between the tub and floor tile in the bathroom is but one place you need to caulk when sealing a tub correctly. Credit: Tim Carter
1. Remove the old caulk
Using a razor knife, you should try to cut away as much of the hardened caulk as possible. The flat razor scrapers used by painters to remove paint from glass work pretty well.
2. Stroke carefully
Make repeated light strokes with the razor knife, not one cut stroke using lots of force. If the knife slips, you can quickly hurt yourself or damage something in the room. You want the tool under control at all times.
3. How to soften it
If the caulk is too hard to cut, it can be softened with liquid caulk removers. These work best if you soak narrow strips of paper towels in the solvent and lay them on the caulk. Then immediately cover the paper towels and caulk with a wide piece of blue painter's tape so the solvent doesn't evaporate. The next day, the caulk should be easy to remove.
4. Leave no dirt
Once the old caulk is gone, clean the tile and tub and dry it. Use small amounts of water and the cleanser of your choice to remove any traces of dirt, soap film, grease and other grime from the tile and the tub. Use white vinegar to remove hard water deposits. All surfaces that are going to receive caulk need to be clean and dry.
5. Where to seal
The places that need caulk are the joints where the tub and tile meet up with one another and where the tile abuts faucets, spigots, shower pipes, floor tile and so forth. Think about where water splashes and where you might see it outside the tub after you use it. All these places need to be sealed so water cannot flow or seep behind walls or under floor tile, or migrate to where it can cause mold and wood rot.
6. Clean and dry
The biggest mistake you can make while caulking a tub is failing to have the surfaces clean and dry. Remember, caulk is just glue. It's sticky. It adheres to things, but if the surface is not clean it will not bond well.
7. Try a hair dryer
Water can get behind the tile and tub and soak the substrate. If this happens, it will be impossible to get the new caulk to dry and cure. You can use a fan or a hair dryer to get the crack between the tub and the tile to dry. If left to dry without these aids, it can take a week or more.
8. Practice
Another big mistake is failing to tool the caulk so it's feathered out well at the edges. The caulk joint should be smooth. Avoid smears on the surfaces. You want it to look like a pro did it. That comes with practice. Try setting up two scrap pieces of ceramic tile at a 90-degree angle and practicing.
9. Use a good gun
It helps to have a fantastic caulk gun. All too often, homeowners use cheap, inexpensive caulk guns. They squeeze the handle and the caulk blasts out of the tube, making a huge mess.
