What you need to know about selecting caulk for use around the house

Q. I'm confused by all the different caulks at home-improvement stores. Can I get by with one type for indoors and one for outside? What's the best all-purpose caulk?

D.L., Atlanta

A According to Ted Anderson, a technical adviser with Gloucester Co., a caulk manufacturer in Franklin, Mass., there are two main types of caulk: water-based (often called latex) and silicone. Each has its own advantages, disadvantages, and special characteristics.

Silicone is waterproof and will withstand harsh elements. It also won't mildew. But on the downside, silicone caulk, which is oil-based, is extremely messy to work with, can't be painted over, and has a terrible odor, he says.

The odor - and accompanying air pollution - is a particular problem indoors. But if you need to seal the inside of a home aquarium, silicone caulk is your best choice.

For all-purpose use, Mr. Anderson recommends water-based caulk, which is easy to apply and clean up.

Some brands have a chemical added to make them mildew-resistant; read the label to be sure. If caulk does mildew, rub it with orange juice or denatured alcohol to get rid of the mold, he advises.

"You get what you pay for in caulk. The more you spend, the better the quality," he says. A canister of good-quality caulk will start at $4 to $5.

You can find out more on the Internet at Jim Evans' caulk page:

www.ghgcorp.com/jevans/MyHomeRepair/caulk.htm and The Natural Handyman's caulk page: www.naturalhandyman.com/iip/inf/infcau.shtm

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