Caulk This Way
We’ve all been there. You walk into the caulking and sealant section of your preferred vendor, and are confronted by a monolithic wall of cartridges—only to choose the same brand and type that you always buy.
“Paint pros tend to like what they like, and end up sticking with something they know rather than experimenting with the new high-end chemistry,” says Jason Toth, technical customer service advisor at DAP. “But there are newer formulations, often for the same price or a small increase, that work under conditions where general-purpose sealers cannot. These sealants dramatically increase performance and help you avoid common problems like cracking and loss of adhesion.”
When it comes to caulks, it’s a matter of striking a balance between adhesion, flexibility, durability, paintability and cost. Across the board, caulk technology has advanced a lot in the past 10 years—with better performance and fewer VOCs and toxic chemicals—but still, the correct caulk selection for the job requires an understanding of the substrates you’re dealing with and the environmental stresses on them.
FORMULAS FOR SUCCESS
Among many painters, acrylic latex caulks are the workhorse for their jobs because of its paintability, broad compatibility with substrates, ease of use, and fast-drying, low-odor formulation. The downside is that, since they’re water based, they’re also prone to shrinking, which can result in cracks. “They’re formulated for places that aren’t exposed to water,” says Amy Burgess, senior channel manager, GE Consumer Sealants. “Prolonged exposure to moisture will tend to dissolve them, and UV exposure will cause the latex to yellow. In a cold environment, the water in the sealant can freeze and the bead may break or lose adhesion.”
Burgess notes that some of today’s siliconized acrylics, another water-based chemistry, have been engineered to be more paint friendly, and won’t cause the paint to crack or change sheen.
High-performance silicone caulks offer good bonding strength and water resistance, but they can be tricky to work with and may cause issues with repairs down the line.
In areas that demand significant flexibility, it’s time to consider an elastomeric caulk. “The difference is that an elastomeric will expand, contract, and recover 100%,” says John Becker IV, president of Creative Material Technologies, Ltd., which manufactures the DynaSolv line of products. “They have memory of where every molecule was when it cured, and when thermal stresses are removed, everything reverts back into perfect alignment. That’s how you get very long-lived caulking compounds.”
John Degirolamo, marketing manager, product application for Henkel, is an advocate for the new generation of silane-modified polymers (SMPs). “SMPs greatly reduce the chances of using the wrong product for the application,” he says. “They don’t contain a solvent, so they’re 100% solid and won’t shrink. They’re also paintable very quickly—even within an hour—and are highly water resistant, right from the start. Plus, you can gun them anywhere from 0º to 140º F and they’ll flow the same.”
For trouble areas with adhesion problems, Becker suggests looking at polyurea caulks and sealers, which are two-component materials. “On a southern exposure, you have a lot of movement, and most caulks will crack,” he says. “It may sound impossible, but the chemistry of new products allows hardness with flexibility.”
WHAT’S IN THE CARTRIDGE?
Reading labels isn’t anybody’s idea of a good time, but it’s essential to understand the basic components of the most common caulks, too. Not surprisingly, the cheaper the caulk, the lower the quality of ingredients used, which can lead to problems like shrinkage. Latex-based products can shrink a lot or contain larger amounts of cheap filler such as calcium carbonate, limestone or marble dust.
“It’s about the ratio,” Degirolamo says. “At the low end, some may have 70% filler, which means less adhesion and flexibility. If I give you a cured bead of that kind of caulk, you can feel the texture and it will break if you pull on it. A higher-quality product with more polymer and less filler will elongate before it breaks.”
For painters, the main issue is usually, “How soon can I get my first coat down?” Like a paint job, however, a successful caulking procedure requires proper prep work and application: –
Clean the Joint and the Substrate. Without a clean surface, you will inevitably end up with delamination and poor bonding. Unless you’re sure what the existing material is, remove everything down to the bare substrate before priming or caulking.
Kill the Mold and Mildew. The north side of a house is a ripe environment for cultures trying to grow, especially if the old caulk has failed. In addition to brushing or spraying a biocide into joints and gaps and letting it dry, you need to consider the formulation of the caulk itself. “You want to look for products that contain a ‘two-pack biocidal system,’ formulated against the biological growth (referred to as ‘bugs’) that can grow in the cartridge as well as after it’s on the surface,” says Becker. “If I have a biocidal material in an acrylic caulk designed to kill bugs before application (while it’s still in the package), and then I apply it, I also need something to prevent surface mold and mildew from forming. But those chemicals need to migrate to the surface—so be aware that enabling that migration through the polymer film may mean you compromise the caulking compound’s waterproofing qualities.”
Practice Your Bead Technique. “We’re all taught to tool the bead to make it look pretty, but the tendency is to tool too much,” says Degirolamo. “On the outside of the house, you want a full 3/8″ bead with 1/4″ adhesion on each surface. On interior jobs, you can get away with smaller beads because it’s more about aesthetics. The main thing is to think of it as shaping the bead, rather than removing and wasting a lot of material. The best contractors I know go right off the gun, pushing the bead in with the tip—they don’t want to tool because it takes more time.”
The Right Caulk in the Right Place. If you’re using 20 cases of caulk on a project and there are two cases of high-end product, it needs to get used in the right place. “Applying elastomeric caulk to a chair rail doesn’t always give you a good return on performance,” says Toth. “If everything is reasonably well anchored, it’s not going anywhere.” Save the elastomeric for the more demanding applications, such as crown molding, where it’s needed.
Avoid Dust. If you’ve got a semi-tacky finish and one of the other tradesmen on site is using a saw, those particles are going to get embedded into the sealant. Make sure to communicate on scheduling.
Read The Label. “Yes, we really mean it,” says Toth. “Labels and formulas change from time to time, so the dry times and other specs might be different from the last time you used the product.” When in doubt, call the supplier to ask questions if you are uncertain about product selection or application.
“A lot of our customers are now considering themselves coating contractors,” says Becker. “When you go with higher-performance products, you set yourself above the lower-end competition that drives your profits down.”
Degirolamo concurs, “Premium contractors need to know the technology that’s available, because their reputation is staked on it.”