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thing. The grey colour that lumber develops as it's exposed to the elements is surface deterioration caused by sunlight and microbes. The cellulose is breaking down under ultra-violet attack and beginning to detach from the underlying wood. That's why it's grey. Look closely and you'll see how weathered wood is often fuzzy. Although this surface is certainly absorbent, it's not physically strong. This means that even though finishing products can soak deeply into old wood, the grip they gain on loose fibers isn't sufficient. The finish layer ends up coming off, along with the wood fibres underneath.

Now that you're wise to the reasons why pre-finishing preparations are vital, I've got some bad news. Getting the job done is a lot of work. Yes, we've all seem those in-store display ads where happy people are obviously gaining tremendous pleasure hosing down their deck with Miracle Wash, or some such wunderproduct. But the reality is that getting ready to finish outdoor wood properly is work. Probably more work than putting on the finish itself. The trick is to do the preparations well, so you don't have to do it again any time soon.

During a five year study, the world's largest finishes manufacturer - Akzo Nobel Coatings - conducted field trials in Canada and the US to determine which pre-application technique maximized the absorbency of outdoor wood surfaces. Chemical deck wash products and mill glaze removers were pitted against pressure washing regimes using plain water and water-plus-cleaning agents. The results of sanding were analyzed, too. The winner? Surfaces prepared with a 60-grit abrasive powered by a walk-behind, square-buff sander yielded the greatest absorbency and surface durability. In fact, the 60-grit surface was nearly 1/3 thirstier than the same wood scoured with a 120-grit abrasive. For vertical surfaces, or areas too confined for a large floor sander, a hand-held random orbit sander is the tool of choice. Bottom line: Sanding new wood is the best way to make your new finish last. It's especially important with any finish that forms a film. Even expensive, brand-name film-forming products will probably peel if applied to wood that hasn't been prepped.

Sanding outdoor wood isn't something most people do before they finish, because it's seems like so much work. Pre-application pressure-washing is much more common, though there are hidden drawbacks to this process. The main one is the creation of surface fuzz on the wood. Pressure-washers deliver

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