What's the difference between latex and silicone caulk, and where should each be used?

The choice between latex and silicone caulk depends primarily on the environment and the movement expected in the area you are sealing.

Latex Caulk (Acrylic or Painter’s Caulk)

Latex caulk is water-based, making it easy to work with and simple to clean up with just water.

• Best for: Interior projects, particularly trim, baseboards, crown molding, and door/window frames.
• Key Advantage: It is paintable. You can apply it, let it dry, and paint right over it so it blends seamlessly with your walls or woodwork.
• Limitation: It is not very flexible and does not stand up well to standing water or extreme temperature fluctuations. Over time, it can crack if the joint moves significantly.

Silicone Caulk

Silicone is a synthetic rubber compound that remains flexible and is completely waterproof.

• Best for: Wet environments like bathrooms (tubs, showers, sinks) and exterior applications (sealing around windows, doors, or siding).
• Key Advantage: It is highly durable, UV-resistant, and maintains a watertight seal even when surfaces expand or contract with temperature changes. It is also mold- and mildew-resistant.
• Limitation: It cannot be painted. Once it is applied, it will repel paint, so it should only be used where the color of the caulk (usually white, clear, or almond) is acceptable. It is also messier to apply and requires mineral spirits or specialized solvents for cleanup.

Summary Rule of Thumb

• If you need to paint over it: Use latex (or a high-quality "siliconized" acrylic latex, which offers a middle ground).
• If it will be exposed to water or is outside: Use 100% silicone.