Caulk is generally less flexible, dries harder, and is designed for filling gaps in stationary joints (like baseboards and trim). It's often acrylic-based and paintable. Sealant is more elastic, adheres strongly to surfaces, and is formulated to handle movement, moisture, and outdoor conditions. Silicone and polyurethane are common sealant types. In practice, the terms are often used interchangeably, but for wet areas or exterior projects, you'll want a true sealant.

100% silicone sealant with mold and mildew resistance is the best choice for shower areas. It remains permanently flexible, adheres excellently to tile and glass, and won't crack under constant moisture exposure. Look for products labeled "kitchen & bath" with built-in antimicrobial protection. Avoid acrylic caulks in showers — they will degrade quickly in constant wet conditions.

No — standard 100% silicone caulk cannot be painted. Paint will bead up and not adhere to silicone. If you need a paintable option, choose siliconized acrylic latex caulk or MS polymer sealant, both of which accept paint beautifully while still offering good moisture resistance. Some hybrid sealants are also labeled as paintable — always check the product specifications.

Drying times vary by product type. Acrylic latex caulk typically skins over in 30 minutes and fully cures in 24 hours. Silicone sealant skins over in 15–30 minutes but requires 24–48 hours for a full cure. Polyurethane may take 24–72 hours to fully cure depending on humidity and temperature. Always check the manufacturer's instructions, and avoid water exposure during the curing period.

For exterior windows and doors, polyurethane sealant or MS polymer sealant are top choices. They offer excellent UV resistance, remain flexible through temperature swings, and adhere strongly to wood, metal, and masonry. If you need to paint the window frame, MS polymer or siliconized acrylic are both paintable options with good outdoor durability.

Use a caulk removal tool or utility knife to cut away old caulk, then scrape the surface clean. For stubborn residue, apply a caulk remover gel (available at hardware stores) and let it sit for 2–3 hours to soften the old material. Clean the area thoroughly with rubbing alcohol or mineral spirits, ensure it's completely dry, and then apply the new sealant. Proper surface preparation is essential for good adhesion.

Mold-resistant caulk contains antimicrobial additives (often fungicides like zinc pyrithione or isothiazolinones) that inhibit the growth of mold and mildew on the sealant surface. These are essential in bathrooms, kitchens, and other humid environments. Even mold-resistant caulk should be cleaned periodically, and if mold grows beneath the sealant, it may need to be removed and replaced.

100% silicone sealant and marine-grade sealants are the only options suitable for constant water submersion (e.g., aquariums, pools, fountains). Standard acrylic and siliconized acrylic products are water-resistant but not waterproof — they will eventually fail if submerged. For projects involving standing water, always use a product specifically labeled "submersible" or "marine grade."

For kitchen countertops, 100% silicone (food-safe labeled) is ideal for areas near sinks and wet zones due to its waterproof nature. For dry areas of the counter that need painting or where appearance matters, siliconized acrylic is a good alternative. Always ensure the product is labeled food-safe or NSF certified if it will contact food preparation surfaces.

Common causes include: using the wrong type of caulk for the application (e.g., acrylic in a shower), poor surface preparation (dirty or damp surfaces), filling gaps that are too large (use backer rod for gaps over 1/4 inch), extreme temperature changes causing expansion/contraction, and UV degradation from sunlight on non-UV-resistant products. Choosing the right sealant for your specific conditions is the best prevention.