Exterior stains: A few go the distance.(Product/Service Evaluation)

Wood siding needs some protection. It shouldn't be left unfinished. Stain can't offer the same degree of protection as paint, since stain soaks into the wood instead of coating its surface. Still, the best of the 23 stains we tested should last about nine years and keep siding from cracking or graying. A high-quality house paint (see page 26) may last a few years longer.

Here's what separates the longest-lived stains from those that deteriorate in five or six years:

Color matters. Compared with paint, stains come in a fairly limited range of colors. But pigment matters in the long-term appearance of a stain (see First Things First, below).

Semitransparent stains let the wood grain show. Less pigment means a shorter life, however, because more of the sun's ultraviolet (UV) rays can penetrate. Indeed, based on our weathering tests, in which one year of exposure equals about three years under normal circumstances, the semitransparents were ready to be reapplied after just two years--or about six years on your home. That's why you won't find any semitransparent stains in the Ratings and CR Quick Recommendations on page 30.

By contrast, opaque stains, also known as solid-color stains, are almost paintlike and should hold up for nine years of actual use. They're the only type of exterior stain we recommend.

Latex lives longer. Our tests of water-based latex and oil-based alkyd products show that latex stains have a slight edge in overall appearance. As the Ratings indicate, the top latex stains tend to keep looking good longest.

HOW TO CHOOSE