Pro Tips for Caulk/Sealant Success
By Tom Matthews
Caulk products serve a number of functions around the home, but it all boils down to filling gaps. Whether you’re filling joints between two materials for aesthetic reasons or you’re filling gaps in your home to prevent air or water infiltration, the application of the product is usually done in the same way.
Not all caulks are created equal, however, and you should pay attention to the properties of the product you purchase. These days, caulking products are made from a wide range of materials, including silicone, acrylic, siliconized acrylics, latex, co-polymers and more.
The easiest and fastest way to achieve a nice, crisp caulk line is to stop by the hardware store, purchase the cheapest acrylic caulk on the shelf, and lay the bead. These cheap caulks are easy to shape and easy to clean up (not sticky like silicone). In practically no time you can fill that crown molding joint and take a photo of your beautiful work. And it’s a good thing you’ll have that photo to remember it by, because within a year the caulk bead will likely dry out, shrink and develop unsightly cracks.
The problem lies in the cheap caulk’s inability to stretch coupled with the the surrounding material’s tendency to expand and contract with moisture and temperature changes. The crown molding moves, the caulk doesn’t, so the bead cracks, looks ugly, and you have to re-caulk it within a year.
To avoid this, choose a better caulk product. Rather than committing to memory the various chemical names for ingredients, pay attention to the indications on the label. Look for words like “elastomeric” and “flexible” which means the bead will bend and stretch in lieu of breaking when the surrounding substrates move. The company Sashco makes a water-based caulk/sealant called Big Stretch that will twist, bend, compress and stretch more than 500 percent of original size.
“Adhesive” is another good characteristic for caulks, especially for application to substrates that are difficult to stick to. If a bead pulls away from the substrate, then the seal has failed, so adhesion is very important.
A high-quality caulk/sealant such as Lexel, which is essentially a liquid rubber, will even stick to wet surfaces.
“Waterproof” sealant is what you’ll need for exterior applications, and “Mildew-resistant” is a crucial characteristic of visible caulk used around moisture-prone areas such as showers and bathrooms.
If you plan to paint the caulk bead, then look for “paintable” on your product package, because not all sealants will hold paint. Although silicone has long been a standard sealant for exterior doors and windows due to its elastomeric properties, conventional silicone sealant will NOT accept paint, and the paint will simply bead up and bleed off the surface. “Paintable” caulks, however, will readily accept a new topcoat in your choice of color.