by Joe Hurst-Wajszczuk

Caulk is a home-improvement hero. No matter how skilled the carpentry, there are always small cracks and gaps that need to be sealed around windows, cabinets, doors, sinks, etc. Caulks help insulate, weatherproof, and pest-proof your home by sealing those gaps. Caulks also excel in cosmetic repairs. Once painted, caulk-filled gaps and cracks disappear, making cabinets, counters and wood trim seem as if they just grew there.

Picking the right caulk can be the hardest part of any caulking job. Most hardware stores carry dozens of different products, each promising better results than the other. If you use the wrong caulk, the joint will fail long before it should, which means that you'll need to do the job all over again. Although some manufacturers now include helpful job-specific labels, others provide little information or overstate their products' performance. Here's how to pick the right product for whatever job is at hand.

CHEMISTRY COUNTS

Despite the dizzying selection, caulks are all made from one of four base, or backbone, polymers: latex, silicone, polyurethane or rubber. The base polymer determines specific characteristics, such as what materials it will adhere to, how easily joints can be smoothed, durability and paintability. Most caulks are sold in long tubes, and you apply them using an inexpensive, hand-pumped caulk gun.

LATEX

Also labeled as acrylic caulk, vinyl caulk or sealant, water-based latex products are the easiest to use, the least expensive and handle the widest range of applications. Latex caulks don't contain volatile chemicals, which means you can smooth joints with a wet finger and clean up excess with soap and water. All latex caulks can be painted, or you can also find a wide palette of pretinted caulks.

Latex-based caulks break into two sub-groups: less expensive acrylics and better-quality "siliconized" latexes. Acrylic latex is fine for sealing areas that won't face major temperature changes or high moisture levels, such as interior windows, doors and trim. Siliconized latex caulks contain a small amount of silanes (a form of silicone) to promote better adhesion. (This is not the same as 100 percent silicone caulk; see below.)