Supex Adhesives & Sealants

DON’T apply sealant over old sealant.

If the existing door frame sealant has hardened and is pulling away, running a bead over it is sure to be an exercise in futility. The old sealant will continue to pull away, taking the new sealant off with it—and before that happens you’ll be faced with a thick, messy seal line that detracts from the look of the window. Scrape off the old caulk with a steel putty knife

DO use a sealant gun with a thumb release.

Cheap door frame sealant guns come with a ratchet-style handle that must be twisted loose to release the pressure on the caulk in the tube. With this type of gun, sealant will keep oozing out until you loosen the handle with your hand, resulting in excess sealant on the window. A better choice is a sealant gun with a thumb release you can press to instantly release the pressure on the caulk so it stops flowing when you’re done running a bead.

DON’T cut too much off the end of the sealant tube tip.

The plastic tip on a sealant tube narrows to a point, and the more you cut off, the larger the bead of caulk will be. Some tubes come with measured cut lines on the tip, allowing you to select the one that most closely matches the width of the seam; others are unmarked. The best practice is to cut off just the end of the tip, and then squeeze out some caulk to see the size of the bead. You can always cut off more, but if you cut off too much at first, your bead will be too thick for the seam.

DO use both hands to run a bead.

It takes two hands to control a sealant gun. Use your dominant hand to hold the gun and pull the trigger, and support the barrel of the gun near the tip with your other hand. Also be sure to keep your wrists straight, moving your elbows and body when running a bead. For example, if caulking a vertical seam, start at the top and as you progress downward, bend your elbows—or knees—to seal lower while maintaining your wrist position. Bending your wrists would alter the angle of the caulking gun, changing the appearance of the bead.

DON’T run a continuous bead from the top to the bottom or from one side to the other.

By the time you reach the end of the bead, you’ll have to change your grip on the  gun, which will affect the uniformity of the bead. Rather, apply from one end to the middle of the seam and stop. Then, start at the other end and caulk to meet the first bead. This will allow you to maintain a steady hand position, which will result in a uniform bead.

DO ride the smooth edge when applyinga seam between a window and textured siding.

Siding is often textured, and if you slide the tip of the tube along the bumpy texture, the bead of caulk will also be bumpy. The solution is to allow the tip of the tube to slide, or “ride” as the pros say, only along the smooth window edge. Keep the tip from riding the textured siding as you’re running the bead. The sealant will still seal the seam and you’ll have a better-looking bead.

DON’T smooth the bead of caulk all the way from one end to the other.

After running the bead, you’ll want to smooth it, either with a wet finger or caulk applicator. The best way to smooth the bead is to start about six inches from the bottom and smooth that small section first. Then, move up another six inches and smooth that section next, pulling downward toward the section you just smoothed. Amateurs often try to smooth the entire bead at one time, which causes excess caulk to build up and overflow on the sides of the seam. Smoothing just a small section at a time will give you a professional look and prevent a mess of excess caulk on the sides of the seam. It takes sealant a couple of hours to start drying, so you should have ample time to smooth in this manner.

DO tape off your seams if you can’t run a smooth bead.

If your hands are shaky or you just can’t seem to move the gun smoothly enough to run a uniform bead, you can still obtain good results by taping off the seam with masking tape. Simply attach strips of masking tape along both edges of the seam, approximately 1/8” away from the seam itself. Then, run the bead of sealant and smooth it off as described above. As soon as you’ve smooth the bead, carefully pull off the tape and you’ll have a perfect 1/4” caulk line.