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Hardest part of caulking is picking best product for job

Caulking, one of the best and least expensive ways to improve the energy efficiency of a home, requires careful choosing of caulking compounds to be effective. Choosing can be difficult because of the variety of caulks offered for sale and a constant stream of new products.

Caulking is generally done on the exterior of a home and can serve several purposes. Caulking for energy efficiency consists of sealing cracks that will allow cold air to penetrate into the home and heated air to escape. Common locations of cracks that need sealing are the joints of windows and doors with siding, siding-foundation joints, and gaps around any pipes and wires that penetrate the walls or foundation of the house. Joints of this type should be inspected every fall to see whether they are caulked, and whether existing caulk has peeled or cracked and needs replacement. Most caulks work best for sealing cracks no more than 1/4-inch wide or deep.Caulks can also be used to prevent moisture from penetrating cracks, and some caulks can be used as adhesives. Cosmetic patching of holes and cracks in wood when painting is another common use of caulk.

Most caulks are sold in cartridges that require a caulking gun to dispense the caulk. A typical cartridge contains 10 or 11 ounces of caulk and will form a 1/4-inch bead up to 50 feet long. Caulks are normally white, but some are clear or are tinted to various colors. Prices range from less than $2 to more than $10 per cartridge. In general, the least expensive caulks should be avoided, because some of them will shrink or crack within a few years. Top-quality caulks sometimes offer long-term or "lifetime" warranties against peeling or cracking.

Caulking guns, often priced at less than $10, are sold at most home centers and hardware stores. It is best to select a gun that includes a lever or mechanism for releasing the trigger and quickly stopping the flow of caulk.

Picking the correct caulk for any project should start with reading the fine print on the caulking cartridge. The label should contain a list of suitable uses for the caulk and the materials it will adhere to, as well as directions for using the caulk.

Following are some of the caulks most useful for do-it-yourselfers:

-Siliconized acrylic-latex caulk. These water-based caulks, which should not be confused with pure silicone caulks, are a good choice for general exterior and interior caulking.

-Silicone caulk. These caulks are solvent-based and have superior adhesion to metal, glass, tile and other smooth surfaces.

-Butyl-rubber caulk. These solvent-based caulks have excellent adhesion to metal and masonry and are sometimes used to patch leaking rain gutters and seal metal flashing around chimneys.

-Foam caulk. This special caulk is sold in an aerosol dispenser can (about $4) and is generally used for cracks or voids too large for ordinary caulk.