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Bathtub Caulking Tips

How to achieve smooth caulk.

FH05JAU_CAUTUB_01-3 how to caulkFamily Handyman
If a lumpy caulk job bugs you, check out these tips to help anyone learn to run a smooth bead of caulk. With advice from a pro painter and a tile setter, you'll soon be caulking everything around the house.

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Overview

I’m always surprised when people ask, “How do you get such a smooth bead of caulk?” For me it seems easy and I usually just reply that it takes practice. But after talking with a painter and a tile setter who both spend a lot of time caulking, I discovered a few techniques that will cut the practice time to a minimum. You can get good results right away. In this article, we’ll show you how to caulk a neat bead around a bathtub, but you can use the same techniques for other caulking as well.

Watch this video to learn how to caulk your bathtub the right way:

A nice bead starts with a well-prepared tip: how to open caulk tube

Photo 1: Cut caulk tube with care

How to open caulk: Cut off the tip of the caulk tube with a sharp knife at about a 45-degree angle. Cut very near the end to make a 1/8-in. diameter opening. Smooth and round the tip slightly with 100-grit sandpaper.

Close-up

Smooth the tip with sandpaper.

The biggest mistake most people make is cutting too much off the tip of the caulk tube. In general, the size of the hole should be about two-thirds the width of the desired caulk joint. Most caulking jobs around the home only require a narrow bead. If you’re caulking woodwork to prepare it for paint, start with the opening very small, just over 1/16 in. diameter. For tub caulking, a 1/8-in. diameter hole is usually about right. Some caulk tubes need to be punched in order to start the flow of caulk. Nails aren’t always long enough. Use a thin, stiff wire like a scrap electrical wire or coat hanger to avoid enlarging the hole at the tip.

You’ll notice 45-degree marks on the tips of some caulk tubes, indicating the angle you should cut the tube. But some pros recommend a blunter tip angle, about 60 degrees. Give it a try. You can always cut the steeper, 45-degree angle if you don’t like it. Regardless of the angle of the cut, the key is to hold the caulk gun at this same angle while you’re filling the joint.

A smooth tip makes a smooth bead. So use a sharp knife to cut the tip, and follow up by smoothing the tip with fine sandpaper (close-up photo). Check out these tips for better caulking, too.

Match your caulking speed to the size of the bead

Photo 2: Prep your caulk gun

Squeeze the handle to start the flow of caulk. Release the pressure as soon as caulk appears at the tip. Then clean off the excess with a damp rag.

Photo 3: Steady your caulk gun

Set the tip at the starting spot. Hold the caulking gun at a consistent angle and keep moving quickly while you squeeze steadily on the handle.

TIP: Align the angle on the tip of the tube to the caulk gun handle. Then tape the tube in place. This way you won’t have to check the position of the tip every time you start caulking.

To apply a smooth bead of caulk that’s just the right size, you have to find the best balance between pressure on the handle and application speed. The trick is to keep the pressure constant and vary the speed according to the size of the joint. To get a small, fine bead of caulk, you’ve got to move the tip along the joint at a rapid clip. Keep the caulk gun at the same angle and try to fill the joint as you go, but don’t worry if you leave a gap. It’s easier to make a second high-speed pass than it is to clean up excess caulk from going too slowly. You can slow down a little for larger caulk joints, but keep the speed steady.

Squeeze the caulk gun handle steadily to maintain an even flow of caulk (Photo 3). Keep the gun moving as you let up and give the handle another squeeze. When you reach the end, quickly lift the tip from the surface and release pressure. Clean excess caulk from the tip before you start a new bead (Photo 2).

Smooth the caulk with your finger

Photo 4: Smooth caulk with wet finger

Smooth the bead using light pressure with a wet fingertip. Clean excess caulk off your fingertip with a damp cloth.

Oops!

Too much pressure and not enough speed cause caulk to ooze out on the sides. Completely wipe off the caulk and try again.

Smoothing not only makes the caulk look good—it ensures good adhesion on each side of the gap. Forget about special tools. Just use the tip of your finger (Photo 4). Wet your finger with water for latex caulk. Then use a wet rag to clean off your fingertip. Rinse the rag often. If you’re using silicone caulk, wear a tight-fitting latex or vinyl glove and wet the fingertip with denatured alcohol. Keep your beads of silicone and urethane caulk slim to make smoothing easier. If you get much excess, they’re hard to clean up and things can get really messy if you keep wiping your finger on the same rag. Use paper towels or a roll of toilet paper instead so you can use a new piece every time you wipe off your finger.

Choosing a Caulking Gun

I’ve talked to pros who swear by the expensive frame-type guns instead of the more common cradle-type (photos below). If you do a lot of caulking, it may be worth spending $15 to $20 for one of these. I admit they work smoothly and are easy to use. But for my money, a medium-priced (about $5) “dripless” gun is the way to go. Look for the “dripless” label on the gun. These are designed to take pressure off the tube as soon as you release the handle so you don’t end up with a river of caulk flowing out every time you set the gun down. I also prefer a gun with a smooth rod, without notches.

Use Masking Tape for Perfect Caulk Joints

It takes a little longer, but the technique shown in Photos 1 and 2 below makes it easy to get a perfect caulk joint every time. This tip is handy if you’re using silicone caulk because cleaning up excess silicone is always difficult. Place two strips of masking tape about 3/16 in. apart where you want the caulk joint. Be careful to keep the lines straight and an even distance apart. Press the tape tight to the surface, especially at grout joints or other depressions, so caulk doesn’t ooze under the tape.

Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

  • Caulk gun
  • Rags
  • Utility knife
You’ll also need sandpaper.

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.

  • Caulk
  • Painter's tape