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Confused about caulk?

Confused about caulk?

Filling cracks with mud and straw may be a thing of the past, but when you consider the bewildering array of caulking products on today's market, you may wish things were still that uncomplicated.

All houses have places where like or unlike materials meet; with the stresses of time and weather, those joints may open up. Even a narrow gap can violate your house's integrity, causing wood rot from moisture seepage in places unseen, or heat loss that drives up your fuel bills.

You'll find there's a caulk for almost any situation--that's why so many different tubes line the shelves. Some have many uses, others are more specialized. An inappropriate or inexpensive caulk will likely need replacing sooner rather than later.

Buying basics: consider shrinkage, flexibility, life span, color, cost

Most caulks are thick like putty, forced from a rigid tube that you load into a caulk gun; guns ($2 to $6) can be plastic or metal. The tubes commonly cost $1 to $15, depending on formulation. You'll also fund easy-flowing tub and tile caulk, in plastic squeeze tubes.

As a caulk dries or cures, it may shrink. Remember, too, that as humidity and temperatures change, building materials (wood especially) will expand or contract. Selecting the right kind will ensure that the seal holds through shifting conditions.

By itself, caulk is generally effective in gaps up to about 1/2 inch wide. Beyond that, or if the crack is deeper than it is wide, fill with backing material--wood or styrene foam (available in sheets).

Some caulks are available in a limited choice of colors or can be painted. For most caulks, painting can enhance performance. Silicone caulks, which come clear or in colors, are an exception--you'll find paintable ones, but these cost a bit more and don't perform as well.

Here's rundown of the common types of caulk and their properties. When you're shopping, read the label for contents to determine the right type. Cost is for a 10- to 11-inch tube.

Acrylic latex. Good multipurpose product indoors or out, though not long-lasting. It comes clear and in colors and can be painted. It flows easily and provides more than adequate flexibility in most situations, but can shrink as it dries. Acrylics don't break down quickly with exposure to sunlight. Normal acrylic latex won't hold to bare metal unless you prime or paint first. "Siliconized' types provide excellent adhesion to metals, glass, and tile; good in bathrooms. Cost: $1 to $4.

Butyl rubber. This does best in sealing metal-to-masonry and metal-to-metal joints, especially aluminum. Superior for areas exposed to moisture, like gutters and downspouts. Provides excellent flexibility, minimum shrinkage. Peel-and-stick caulk pictured on page 148 is butyl rubber. Sold in colors; paintable. Cost: $3 to $4.

Ethylene copolymer. Multipurpose type that adheres to most materials, except some plastics. Comes clear and in colors; paintable. Provides superior flexibility for joints susceptible to movement. It's usually self-sealing if punctured but can be tacky, difficult to apply. Good around windows, doors, and aluminum siding. Cost: $4 to $5.

Latex, polyvinyl latex. Bonds well to most surfaces; not good with aluminum or glass. Available in colors; paintable. Dries semirigid; good for dry areas that don't expand, contract, or vibrate such as interior wall joints. Cost: $2 to $5.

Polyurethane. Durable type that adheres to most materials, except some plastics. It has excellent resistance to sunlight, bonds well to masonry and concrete. It's not good in moist conditions, and you have to prime porous materials before use. Comes in colors; check label for paintability. This is a good caulk for concrete and aggregate patios and garage floors. Cost: $5 to $7.50.

Silicone, silicone rubber. Good with most materials, but not with surfaces to be painted. Has excellent flexibility but won't bond to oily woods like cedar, cypress, or teak. Prime porous surfaces before using. Superior water resistance makes it good around tubs and bath fixtures, windows; of all caulks, silicone best withstands extremes of heat and cold. Comes in limited colors; not paintable. Cost: $3 to $7.

Toluene/naphtha/alkyl acetate. Called Lexel, this new product comes in a clear tube, dries slightly clearer than silicone. Suitable for most materials, including plastic and vinyl. Has good flexibility, is paintable, and withstands exposure to sunlight. Works well with glass and acrylic plastic. Cost: $6 to $8.

Urethane foam. Has properties similar to polyurethane. Sold in aerosol cans; easy to apply, dries rigid. Very sticky; gloves are a must. Works best in wide gaps; foam expands to nearly triple its volume to insulate and stop air infiltration. Comes in white but tends to yellow; must be painted with acrylic latex if the sun will hit it. Cost: about $6 for a 12-ounce can.

Best way to apply

Clean surfaces of old caulk, dust, dirt, and any loose or flaking material such as paint or splinters. If necessary, use a primer to seal the materials before caulking, as advised on the label.

For the best flow, make sure the caulk is at room temperature. Cut the tube nozzle at a 45| angle with a sharp blade; where you cut determines the size of the bead.

Load the caulk gun and squeeze the trigger a few times to put a little pressure on the plunger; be careful, though, or the caulk will flow freely before you're ready.

Hold the gun at a slight angle to your work and draw out a full, round bead. To smooth out the bead and better fill the crack, dampen a finger, butter knife, or the back of a small spoon and slowly draw it over the caulk (for silicone, dip the spoon in soapy water).

Have a clean cloth and some soapy water close by for cleanups. You can also protect adjacent surfaces with strips of masking tape, although removing the tape can mess up your tidy work. A single-edged razor is also handy once the caulk is dry. If you're going to paint, follow label directions for the caulk's curing time. This may take 30 minutes to 2 hours--or even a day or more--depending on the product, the temperature, and the humidity.

Some tubes are sold with close-up caps. A cap or a large nail can preserve some types after opening, but others will set up hard right in the tube regardless of seal.

Photo: Small tube is easy to control. For aluminum gutter parts, use silicone caulk; butyl rubber would also work

Photo: To patch masonry wall, try acrylic latex; it provides good flexibility, withstands exposure to sunlight, takes paint well

Photo: Urethane foam in aerosol can expands rapidly to fill wide gap. Foam is sticky, hard to clean off hands, so wear gloves

Photo: Neat peel-and-stick caulk takes quick care of tubs. Peel backing, position strip with beveled edge down, press in place

Photo: Finger trigger controls flow of white silicone caulk through needlenose tube. Or try acrylic latex for tubs

Photo: See-through tube of Lexel multipurpose caulk, new on the market, lets you monitor your supply. Bead dries clear

Photo: Now what? Overwhelming choice can leave you cross-eyed and confused if you're not sure which type you need
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Copyright 1987 Gale, Cengage Learning. All rights reserved.

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Date:Nov 1, 1987
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