Techniques for caulking

Existing caulk (especially silicone and poly) must be completely removed before new caulk can go on. Use a sharp utility knife or a narrow chisel, and brush or vacuum out all loose debris. Rubbing alcohol removes soap scum on tubs; a blow-dryer set on low will dry up damp joints.

Caulking guns. There is a difference in caulking guns. Look for heavier-gauge metal, a built-in cutter for the tip of the tube and an integral steel pin for puncturing the seal. Most pros prefer a solid-shaft gun that advances with a cam over the notched-shaft type, citing more even pressure on the piston, which results in a smoother bead. These guns cost $5 to $7 each.

But not all jobs call for a gun; there are two other types of dispensers that can make a job easier. For example, 5-oz. squeeze tubes are great for small, interior jobs. And 7-oz. pressurized cans let you lay down a uniform bead when working with only one hand, such as when caulking overhead.

Getting ready. Before you open the tube, make sure the temperature and conditions are right for application. "When the weather turns cold, I take my caulk out of the truck and store it indoors,"explains Jeff Younkin, a remodeler based in Bethlehem, Pennsylvania. "Many caulks are difficult to work in cold weather, so it makes sense to keep them warm as long as possible."The working temperature range of caulk varies by type; check the label.

Another important factor in application is how you cut the tip of the tube. The biggest mistake is cutting too far down, creating an opening that's too big. The opening should be slightly smaller than the bead you'll apply. Also, cut the tube at an angle (up to 45 degrees); some pros use a nearly straight cut, arguing this makes caulking into interior corners easier.

If the crack you're filling is deeper than 1/2 in., you must wedge flexible backer rod (available where caulk is sold) into the joint so the caulk is limited to a depth of 3/8 in. The ideal width for a bead is also less than 3/8 in. It's easy to ignore this step, but the price you'll pay later is an open caulk joint.

Letting it flow. If you're not confident of your caulking skills and are laying down a bead that will show, consider applying masking tape to both sides of the joint before caulking. Then remove the tape as soon as you've finished tooling. When caulking, keep the gun (or squeeze tube) moving so you leave an even bead. You can either push or pull the tube, whichever is most comfortable for you. As you near the end of the joint, press the release lever on your gun (or withdraw the piston slightly) to stop the flow of caulk. When applying a long bead, break it up into shorter sections. "I often apply and tool just several feet at a time,"says Younkin. "I get one section to look the way I want and then move on to the next."

Tooling. Be extra cautious about overapplying silicone and polyurethane caulks because these sealants are difficult to tool and messy. Tool butyl, silicone and polyurethane caulks with a caulking tool or a plastic spoon. (Water-based caulks can be tooled with a moistened finger.) Standard-cure silicone is tricky because it's very sticky and must be cleaned up quickly -- once cured, silicone yields only to a razor blade.

For smooth results with butyl and polyurethane, make sure to dip your spoon or tool in solvent. Also have the proper cleanup gear handy: a moistened sponge if you're using water-based caulk, or solvent and clean rags with other sealants.

The replaceable tip that comes with some caulks can be used to seal a partially used tube. But caulk will still harden in the tip. If you're lucky, your first few trigger squeezes will push the hard material free, but often it requires the help of a 16d nail or the purchase of a new tube.

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