Make sure the caulk you apply for your next project dries and cures completely to achieve long-lasting results.
By Andreana Lefton, Bob Vila
Q: My bathtub sealant needs a refresh, and I’ve decided to re-caulk the tub myself. How long does caulk take to dry before it’s ready for use?
A: There’s nothing like fresh caulk—a waterproof filler and sealant, used in home construction and repairs—to give your bathroom a bright, clean look and feel. Over time, moisture can erode even the best sealant, allowing mold and mildew to form. Despite bleach and scrubbing, dinginess can persist, so replacing the caulk is a smart move. But if the caulk isn’t allowed to fully cure, it can more easily wash away, ruining your hard work and leaving joined surfaces open to water damage.
Understand that there’s a vital distinction between “dry time” and “cure time” when it comes to caulk.
In general, silicone and acrylic latex caulk can be dry to touch within 30 minutes of air exposure—depending on how humid or well-ventilated your space is. But it can take one to 10 days, depending on the formula, for the caulk to fully set or cure—in other words, become completely waterproof and ready for use.
Start with the right caulk for the job, which will have unique dry and cure times.
There are three types of caulk for common household surfaces that receive a lot of moisture—like tubs, showers, and sinks:
- Silicone caulk works best with glass, metal, and ceramic because it adheres easily to smooth, nonporous surfaces, creating a flexible yet long-lasting bond. Silicone caulks with antimicrobial additives are now available, great for keeping germs at bay in bathrooms and kitchens.
- Acrylic latex caulk is best for filling small gaps and joints in wood, especially areas that will be painted and not exposed to much water. This is because acrylic latex caulks can shrink or crack over time, leaving surfaces open to water damage. Some acrylic latex caulks now have silicone additives to improve flexibility, durability, and waterproofness—making it appropriate for tub and sink use.
- Polyurethane-based caulk is growing in popularity, especially for outdoor uses and window seals. Polyurethane is paintable, provides greater elasticity, repels dirt, and creates a watertight seal. It does take longer to cure than silicone or latex caulks, however.
Play it safe, even with “fast-drying” formulas.
Some silicone caulks are advertised as “fast-drying,” claiming a one-hour dry time, but read the fine print before planning your project based on this information: It may be that the ideal drying conditions for this rate are a narrow range of temperatures and humidity levels. Budget at least three to 12 hours for these products to dry and a full 24 hours to cure. For latex-based products, 24 hours is also recommended before water exposure. Polyurethane caulks can take up to 10 days to cure fully.
Consider if the caulk can be painted.
If you intend to paint over caulk—for example, if you have tile molding in your bathroom, separating a tiled backsplash from a painted wall—you’ll find caulk that’s formulated to continue curing beneath a coat of paint. With these products, you can typically apply paint after 30 minutes, whereas with polyurethane caulk, you must wait seven to 10 days until the surface is cured before painting. Whatever formula you choose, be sure to read instructions thoroughly, as each manufacturer has different formulas, with optimal methods for application and drying.
Understand how your formula reacts to moisture.
An acrylic latex-based caulk dries as water evaporates from the material, so placing a fan in the room will speed up the process. In contrast, silicone caulks actually need moisture to dry and cure—a humidifier in the room is an asset. Polyurethane caulk should not be exposed to any direct water or added moisture for at least three days to a week.
The temperature will impact caulk’s drying time.
The ideal temperature for applying and curing caulk ranges between 40 and 80 degrees Fahrenheit, so adjust your thermostat accordingly. If caulking in winter, when the air is often drier, it may take silicone longer to cure—but don’t try to speed the process by adding heat (e.g., with a hairdryer), as heat softens and can potentially melt silicone. Latex will freeze in extreme cold, and frigid air lacks enough moisture for proper polyurethane curing, so avoid using it in freezing temperatures.
Use fresh caulk for the best results.
Older silicone and latex caulks can deteriorate in quality, even inside a sealed tube, and never fully cure. Most companies will put an expiration date on the caulk tube, but if you have a tube of undated caulk lying around, you can play it safe and buy a new one or test a strip on a solid surface first. You should notice a firm “skin” begin to form within 30 minutes if the caulk is fresh. Polyurethane caulk should be used within 12 months of manufacture date.
