The Latest News on Caulks and Adhesives

Visit a home supply store and you’ll find many different caulks for many different jobs, but it’s important to sort out the differences. When properly applied, a top-quality sealant helps provide a watertight and airtight seal to increase energy efficiency and protect the entire home from moisture damage. The right caulk can provide years of low-maintenance performance, but the wrong one can fail to seal or even serve as a breeding ground for mildew.  

For example, a common gripe about bathtubs and showers is the dark mildew stains that often appear along the joints. The mildew is probably due to using the wrong type of caulk in a wet environment. Check the store for the variety of caulks labeled explicitly for “tub and shower” or “tub and tile.” These “tub and shower” caulks are likely silicone-based, which makes them ideal for damp situations. Silicone sealants are flexible when they dry and often contain a mildewcide. Pick up one of these products for a bathtub job, but do not save the rest to use in your kitchen if it contains mildewcide. The mildewcide is a poison that shouldn’t be used around food, drinking water or in dishwashers. This is why it’s important to always check the label for instructions.  

Silicone is the ingredient that serves as a selling point for many sealant products. Unlike acrylic latex caulk, 100-percent silicone is waterproof as long as it remains adhered to the substrate. Water cannot get through it or break it down. Once cured, there is no shrinking, hardening, cracking or crumbling. Even extreme temperatures, which often cause acrylic caulk to lose flexibility and degrade over time, do not affect silicone.  

Silicone is also shrink-proof and flexible once it has cured, so it stretches and compresses with joint movement as a house moves and settles. This eliminates hardened acrylic caulk that can break over time, leaving gaps for air and water to pass.  

Given all the benefits of silicone, you might wonder why acrylic latex caulk is still going strong. If water isn’t an issue and you plan to paint over the caulk, then acrylic is a better choice. For indoor jobs, acrylic caulk has some big benefits going for it: namely, affordability, workability and paintability. Acrylic caulk is usually half the price of the silicone variety, which amounts to major cost savings on large projects.  

Acrylic caulk can also be easier to work with because it isn’t nearly as sticky as silicone. A quality acrylic caulk applies smoothly and easily, and you can run your finger over the bead to shape it without covering yourself in a gooey, viscous mess that refuses to wash off. Instead, a good acrylic caulk will wash off with water and work more like cake frosting than glue, preventing the “rabbit in a tar pit” effect.  

The cleanup factor is why many manufacturers’ claims of an “all-purpose” siliconized caulk can be misleading. I suppose it’s true that the silicone variety can potentially be used anywhere, but the extra time and work involved in the cleanup makes the product impractical for large, interior jobs where waterproofing isn’t necessary. And when I say cleanup, I don’t mean cleaning once at the end of the job. The cleanup for silicone will likely require many repeat trips to the sink to wash up during application, because if you don’t immediately use mineral spirits to remove the silicone, you will soon be coated with cured sealant—and you practically have to sand-blast the stuff off.  

Another important factor is that acrylic caulk is paintable, and thus is commonly called “painter’s caulk.” Although a few of the newest formulations of silicone sealants are advertised as paintable, paint typically will not adhere to silicone. Again, be sure to check the packaging for recommended usage. Silicone sealants are usually sold in white or clear, but some manufacturers now offer black, bronze, almond, gray or cedar.  

Acrylic caulk works great for interior applications that need to be painted. In this photo we’re caulking a baseboard with one of DAP’s new Pro Caulk tools.

Also available are hybrid caulks, such as DAP’s Alex Plus Acrylic Latex Caulk Plus Silicone. The silicone adds flexibility and durability while the caulk remains paintable and easy to clean up.