When it comes to caulking, there are as many different types of caulk as there are places to use caulk. Selecting the right product for the job is the single most important step of any caulking project.

• Choose silicone caulk for exterior applications where flexibility and durability are important. Silicone caulk adheres well to glass, tile and metal but does not stick to wood or painted surfaces. It is very flexible, can fill gaps up to one-half inch wide and holds up well under extreme weather conditions. On the other hand, silicone caulk is challenging to work with, difficult to remove and will not stick to existing caulk materials in repair situations. Never use silicone caulk in place of glazing in windows or in areas where it may come in contact with food or drinking water.
•  Choose acrylic latex caulk for most home repair projects, both inside and out, where clean up and ease of application are a priority. Acrylic latex caulk is very easy to work with, cleans up with soap and water and adheres to most surfaces. These caulks can be painted over and work well in both interior and exterior applications. Once cured, acrylic latex caulk can stand up to most weather conditions, but unlike silicone, which cures rapidly, acrylic latex caulk can take several days before it reaches optimum durability. Do not use acrylic latex caulk in areas where movement or moisture are abundant.
• Choose butyl rubber caulk for repairing gutters and sealing around chimney flashings or in other exterior applications where moisture is present and adhesion is challenging. Butyl rubber caulk is extremely water resistant and flexible and adheres well to metal, brick and stone. It is very messy and never hardens completely. 
• Choose polyurethane caulk for repairs in high-traffic areas such as driveways, sidewalks and garage floors. Polyurethane caulk is stringy, smelly and potentially hazardous to your health. Use it with extreme caution, in well-ventilated areas while wearing rubber gloves and a respirator.
• Choose synthetic-rubber caulk, like Sashco’s Lexel, for applications where joints will expand and contract over time. Synthetic-rubber caulk is extremely flexible, can be applied in most weather conditions and is paintable. It is also highly flammable and will shrink significantly. Because of its high percentage of volatile organic compounds, or VOCs, synthetic-rubber caulk should only be used on exterior applications.