Caulk, Caulking Guns
by Jeff Woodard
Some caulking manufacturers claim the life span of their products will last at least 10 years. Others say that their materials will hold up 20, 30, even 50 years.
to improve product integrity and performance, some caulking manufacturers claim the life span of their products will last at least 10 years. Others say that their materials will hold up 20, 30, even 50 years. Are these numbers valid? While the proof may be in the caulking, it also lies within the ability to select the proper product and to apply it correctly.
Dave Siegner, president of Siegner and Co., a commercial painting contracting firm in Portland, Oregon, says he has seen proof of 10-year durability. “We’ve repainted over caulk that’s been in place over 10 years, and have found that, if it was a premium caulk — with plenty of elasticity, installed over properly prepared and clean surfaces, and with a lot of resiliency to withstand thermal shock and surface movement—it didn’t need to be replaced.”
Siegner is skeptical of advertising that bills certain caulks as durable past 20 years. “I would be very cynical of their longevity, but certainly not of their marketing appeal. One exception, he notes, is the product his company uses most: White Lightning 3006, “a 40-year, 100% acrylic siliconized latex caulk.”
Under “ideal” conditions, the 10- and 20-year caulks hold up, says Steve Holland, national accounts manager for Sashco Sealant, Co. in Brighton, Colo. But, he adds, “Unfortunately, ‘ideal’ conditions’ usually are not there. Basically, longevity has to do with the amount of filler in the caulk. The more filler, the less flexibility. The less flexibility, the less durability.”
Tom Kehr, national accounts manager for Lighthouse/VIP Products, a division of General Electric Sealants and Adhesives based in New Smyrna Beach, Fla., says his company conducts “exhaustive testing under extremely harsh conditions to analogize the very worst possible conditions. From there, we then accelerate these conditions, which give us a very clear view of the product’s performance over a particular period of time.”
Chemical bonds, polymer structure and silane (an adhesion promoter) help caulk adhere to a variety of substrates, says Holland. Clean substrates are key to caulking longevity in common situations such as working with wood base, casing and crown moulding in new construction.
“If the joints that are going to be caulked - generally where the trim meets the drywall, or the joint between multiple pieces of moulding - are not properly cleaned, the caulk will stick to the contaminants present in the joint,” according to Kehr. “Common contaminants in this situation are drywall dust, sawdust and dirt.”
Kehr says curing is the key to a caulk’s ability to stick and be effective. “What basically takes place is both a chemical and a mechanical process that progresses as the caulk or sealant goes through its curing process. The ability of the manufacturer to formulate different types of caulks and sealants is a key,” says Kehr. “Different substrates present different issues when it comes to caulks and sealants. It is always best to check with the manufacturer on particular and specific applications.”
Reactive, two-part caulkings are best at eliminating shrinkage, says Holland: “All one-part caulks will have some shrinkage.” Kehr notes that shrinkage in latex or acrylic latex caulks are “simply part of the chemistry. However, what may be viewed as a flaw in the caulk or sealant may, in fact, be an inappropriate application of the product. To further exacerbate the situation, many times the substrate— such as the case of wood trim—may also shrink.”
Every caulk and sealant will have its own specific abilities and limitations. “In addition,” says Kehr, “each individual product may be designed for a specific purpose (e.g., interior trim), or may be designed for more general and varied (interior or exterior) usage.
One unpleasant result from too much shrinkage is water penetration. Knowing the difference between “water-repellent” and “waterproof” is helpful, says Kehr.
“ ‘Water repellent’ essentially means the ability of a product to shed or sheet water away for a period of time or a particular circumstance. However, at some point in time, or under certain circumstances, the product may lose some or all of its ability to shed or sheet water away. ‘Waterproof,’ on the other hand, means the ability to actually prevent water from entering,” says Kehr.
When water enters a poorly covered surface, washout can occur. Other results of substandard applications include tearing, cracking and loss of adhesion caused because the surface was painted too soon after caulking. “The single largest problem we see is misapplication of the product,” says Kehr. “This can mean anything from application over a poorly prepared substrate, to misuse of the product; to not using enough caulk in a joint; to simply not choosing the appropriate caulk for a particular use.”
Siegner says the most problematic caulking applications for his company are those installed by others at joints found on new, tilt-up concrete construction projects. “The material used is typically a two-part urethane product. Since the new VOC regulations have gone into effect, we’ve had several failures despite waiting for the recommended cure time. We now wait for twice the time and wipe the caulk joint with Xylol prior to painting.”
Silicone is a significant factor in today’s caulking market. “Silicone additives in a latex caulk give improved adhesion,” says Morton Jones, a chemist for DAP, Inc., of Baltimore, MD. “It does an outstanding job with many different types of substrate such as glass, cement mortar, concrete and ceramic tile.”
Dave Fuller, vice president of marketing for DAP, says adhesion and flexibility are the most critical components of caulk. “Our 100 percent silicone caulk is a product that we introduced last August, and it combines the best of two worlds,” says Fuller, referring to silicone’s flexibility and latex’s properties that improve its paintability.
Elastomeric caulk is another product offering distinct advantages. It contains polymers with elastic properties resembling those of natural rubber. “It is highly flexible and is best used in an expansion area or in an area exposed to extreme weather conditions, such as exteriors,” says Morton.
According to Kehr, elastomeric caulks should be used when product is expected to withstand the harshest, most severe conditions. “However, because there is a significant difference in what manufacturers may define as elastomeric, it is best to research the specific applications and limitations recommended by the manufacturer,” he adds.
Ideal applications for elastomeric caulk, says Siegner, include exterior applications, “where the surface is expected to continue moving or shifting. It has a greater elongation factor than most latex caulks.”
Colored caulking is another enhancement of applications, though it is “purely for aesthetics,” says Holland. The advantage is that “if a caulking is a close match to the surrounding surface, it doesn’t have to be painted.” Adds Siegner, “It can be used for touch-up purposes without having to paint over it.” Lighthouse VIP is able to custom-match the color of its caulking to the paint, according to Kehr, thereby saving labor costs of repainting.
The general consensus is that it is best to prime first, then caulk. “That way, the first coat also serves as a primer for the caulk,” says Holland, who is skeptical of some painters’ claims that caulk can be painted within 20-30 minutes of application. “One needs to wait about a day with the better, long-lasting caulks. Painters’ caulks are loaded with filler, which will have much less flexibility and thus can be painted in a shorter time period. Good acrylic caulks take longer, but will last much longer.”
Kehr agrees. “The longer one can wait, the better. First and foremost, temperature and humidity have tremendous bearing on the speed at which caulks cure. The temperature and humidity at application, and shortly thereafter, will play a significant role in the caulk’s ability to ‘cure.’ ”
An additional key element in the application of caulking is bead size: How large a bead can be applied before strength and durability are compromised? “In theory,” says Holland, “ caulking has no limitations, and with proper joint design, a bead can be several inches wide. Sashco manufactures several products to the log-home industry, and it is not uncommon for beads to be 6” to 8” wide. Backer rod is essential for larger joints. For joints 1” or more in width, the depth should be 3/8” to ”. Depth of joints less than 1” should be half width, but no less than inch.”
Elimination of unsightly “snail tracks” is also a primary goal in successful caulking applications. “These can be caused by an extremely small hole cut in the nozzle,” says Holland. “Painters will often make smaller holes in the nozzle for some of their applications. To avoid snail tracks, the painter simply needs to cut a larger hole in the nozzle.” Using a high quality caulk also helps to avoid this problem.
As the relationship of caulking and painting continues to evolve, the role that each plays becomes more crucial.
“I feel that one of the largest areas for improvement in the relationship between paint and caulk should be focused at the manufacturing level,” says Siegner. “Paint is intended to be a protective coating. Its ability to be decorative is secondary. Caulking has its place and purposes as well, but neither is designed to be compatible with each other in all applications, particularly outdoors.
“We feel strongly that there is an appropriate top-quality choice for any given situation. Caulk is a very small expense for us in the larger picture, but the problems a client may experience due to using cheap or inappropriate materials is far too detrimental to our business relationships to risk such a minor cost savings.”