Choosing the right caulk
Even though there are now more different types of caulk and sealant available than ever before, it's actually easier to find the right product. In a welcome change, many manufacturers use large, job-specific labels on cartridges and tubes. You don't have to read the fine print to learn about recommended uses. But it's still important to understand which basic type of caulk is being offered. For one thing, chemistry has an impact on the broad price range you'll see in the caulk aisle: A 10-oz. cartridge costs from $1 to $7.50 or more. Chemical content also determines some important general characteristics, such as how easily caulk joints can be shaped, or tooled, whether a caulk can be painted and how durable it is.

New caulks are always hitting the market, so knowing something about their chemistry can signal how big an advancement a new product really is. For example, the downside of silicone caulk is that you can't paint it. But DAP's Paintable Silicone Sealant is a true water-based silicone caulk that can be painted. It's also easy to work and odorless. And instead of using mineral spirits to clean it up, you can use soap and water. Here's a look at the four types of caulk.

Rubber caulks. These products are made with rubber compounds like butyl, isoprene, butadiene, nitrile and styrene. Rubber caulks typically offer good adhesion and excellent water resistance; you can even apply them to damp surfaces. But their solvents are highly flammable and dangerous to breathe, so don't use these caulks indoors. Rubber caulks are especially sticky and difficult to tool, and they will shrink as they cure. Without any tooling, a round bead will dry fairly flat.

Latex caulks. Also labeled as acrylic or vinyl caulks and sealants, these water-based products are the easiest to use, will handle the broadest range of applications and are often the least expensive. However, many latex caulks aren't as durable as more expensive options. "Siliconized" latex caulks contain small amounts of silicone for improved durability and adhesion.

Latex caulks don't contain volatile solvents that pose fire and health hazards, and joints are easy to tool. But avoid removing too much material when tooling, because shrinkage will further reduce the width of the caulk joint. A broad range of colors is available, including hues that match most plumbing fixtures. Water-based caulks can be also be painted.

Silicone caulks. These products stay flexible at all temperatures, are completely waterproof and adhere to a wide range of materials. They are excellent all-weather caulks that can also be used in wet indoor locations, primarily around tubs and shower stalls. However, because silicone is expensive and offers poor tear and abrasion resistance, it's not a good choice in high-traffic areas. Except in water-based versions, this family of caulks is unpaintable and difficult to tool. Among solvent-based silicones, caulks or sealants labeled "neutral cure" or "odorless" are preferable because they don't give off any unpleasant odor as they cure. Plus, the acetic acid produced as "smelly" silicones cure can corrode certain metals and masonry surfaces.

Polyurethane sealants. Just like polyurethane varnishes, this family of caulks and sealants is superdurable. Abrasion and tear resistance are superior to silicone, and the caulk is highly adhesive, waterproof and flexible. Shrinkage is minimal, and most polyurethane formulations can be painted or stained. Because it's expensive, this caulk should be used sparingly -- only where strength, durability and weather resistance are important. Tooling is messy and difficult, and you need to clean up with solvent.

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