When it comes to caulk, the conventional wisdom is that there are three basic kinds: acrylic, alkyd and silicone. To seal small gaps in the bathroom, you use a waterproof silicone caulk, which can close up tub and sink surrounds and bridge gaps in tile transitions. Most silicone caulks are not paintable. For interior woodwork, like where crown molding meets a wall or ceiling, or the corners where an imperfect miter joint allows baseboard ends to separate, use premium acrylic, which can be painted. The problem is that for many areas, such as around windows or doors, you want a caulk that will expand and contract and is paintable.

In the past it was difficult to find a caulk that stayed flexible and is also paintable. But today’s hybrid formulas combine the two materials, figuratively closing the gap in their performance differences. A product like Benjamin Moore’s Crown and Trim Sealant 464 which is a blend of acrylic and urethane or 50 Year Siliconized Caulk 466 pairs the paintable finish of an acrylic with a urethane or silicone’s flexibility to expand and contract as moisture changes. The blended characteristics make them ideal for a job like a window surround—applied between the wood casing and the drywall inside (or to seal the window frame against siding outside), a siliconized latex can keep a watertight connection as the wood shifts with the weather. It won’t shrink or crack, and it can be painted after it’s applied. In addition, the urethane or siliconized mix can also stick to a wider range of substrates than a pure acrylic or silicone product. Both the 464 Crown and Trim Sealant and 466 50 Year Siliconized products will work in every room in your home and keep your final paint job looking better longer. The 466 can be used for both interiors and exteriors, on wood, metal, brick, concrete, or tile. Other significant evolutionary improvements include a lower VOC content, an additive to resist mildew, and a manufacturing process that uses vacuum-packing to eliminate bubbles and ensure a smooth, consistent product.

But a few important caulk characteristics remain the same, especially regarding application techniques.

• If you are applying the caulk to a bare substrate like wood or drywall you should prime these areas first.
• No caulk can be sanded after it cures so its important to lay a proper bead to begin with: With the caulk tube’s nozzle cut at a 45-degree angle to open a 1/8-inch-diameter hole, use steady pressure to squeeze a thin line over a few feet of a cleaned surface.
• Smooth it down with a damp sponge, rag, or a tool (a popsicle stick works well), then move on only when the work looks finished. A good bead should measure between 1/8-inch and 1/4-inch thick, and should go between 1/8-inch and 1/4-inch deep.
• Remove the excess before the fresh caulk skins over—after that, it’s set. Do the job when the temperatures are above 50 degrees and the humidity is low. The bead will dry to the touch in less than six hours, but give it three days to cure before coming back with the paint.