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Double the life of outdoor paints and stains
By Steve Maxwell
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Less than twenty years ago my friend Mike built a large, cedar-clad house with a spacious cedar deck. He loved outdoor wood back then, now he hates it. Part of the reason is a lack of understanding about how to finish wood properly. Mike tried a handful of finishing products over the years, including brands with the most recognizable names on the market today -- all with disappointing results. He’s torn down the deck (it was already starting to rot) and replaced it with a much smaller version. Now he’s even talking about vinyl siding. As far as Mike’s concerned, wood should never be used outdoors. Ever. Is he right? Can anything be done to finish outdoor wood durably?
Sun, rainwater and foot traffic all conspire to make outdoor wood surfaces the most challenging of all to keep finished. Your secret weapon is a series of counterintuitive steps that are so easy to miss almost no one puts them into practice. And that’s too bad because the pay-off is worth it. Any way you slice it, keeping outdoor wood stained, painted or sealed is a lot of work, so you might as well get the most mileage from the time you spend on your hands and knees. And it all begins with an obscure bit of information about lumber.
The first thing to understand is that new wood is a poor candidate for finishing as it comes from the lumberyard. And the reason is something called ‘mill glaze’.
Every piece of construction lumber in the world is prepared using a two-step process. First comes the saw blade that slices round logs into rough lumber. Next is the planer. It uses high-speed revolving knives to shave the surface while smoothening it, bringing the wood down to standard dimensions. And while this is excellent and necessary, planing also imparts a slightly burnished surface to the wood, preventing full absorption of film forming finishes. This is the problem. When paints, stains and tinted varnishes can’t get a good foothold into the pores of the wood, they peel way too soon. This is the danger, but it can be avoided.
The trick is removing the mill glaze before finishing begins, and there are two ways to do it. The first and easiest is to slosh some mill glaze remover onto the wood, let it sit as directed, then rinse it off, ideally with a pressure washer.
While this procedure does remove some of the burnished surface that inhibits finish absorption, there’s a second step that makes wood even thirstier. If you have the time and inclination, consider sanding your outdoor wood when it’s fully dried after the chemical mill glaze treatment. This job can be simply tiring or absolutely unbearable, depending on the sander you’ve got.
Give yourself every chance for success and use a 5 or 6-inch diameter random orbit sander with a 60- or 80-grit disk installed. Forget the little quarter-sheet finishing sanders (they’re too weak) or the hand-held belt sanders (they’re too unwieldy for this job). Sand, vacuum, then finish knowing you’ll get the best possible mileage from the coating you apply. Today’s top products last as long as 36 months on a deck, the worst will need maintenance in a year.
Do you have weathered, thirsty outdoor wood you’d like to finish? You certainly don’t have a mill glaze problem, but there is something else you need to consider. When wood goes gray, it means that surface fibres are being broken down by sunlight and water. And while these fibres are very absorbent, they’re also weakly attached to the underlying wood. That’s why gray wood needs to be sanded, too. It removes loose surface fibres that would otherwise detach from the wood underneath, letting the finish go with it.
Maintaining paint or stain on outdoor wood involves work. That’s part of the price you pay for this material, but it needn’t turn you sour. Tackle the prep work right and you’ll have plenty of time to enjoy the beauty of your outdoor wood, too.
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Double the life of outdoor paints and stains
By Steve Maxwell
|
|
|
Less than twenty years ago my friend Mike built a large, cedar-clad house with a spacious cedar deck. He loved outdoor wood back then, now he hates it. Part of the reason is a lack of understanding about how to finish wood properly. Mike tried a handful of finishing products over the years, including brands with the most recognizable names on the market today -- all with disappointing results. He’s torn down the deck (it was already starting to rot) and replaced it with a much smaller version. Now he’s even talking about vinyl siding. As far as Mike’s concerned, wood should never be used outdoors. Ever. Is he right? Can anything be done to finish outdoor wood durably?
Sun, rainwater and foot traffic all conspire to make outdoor wood surfaces the most challenging of all to keep finished. Your secret weapon is a series of counterintuitive steps that are so easy to miss almost no one puts them into practice. And that’s too bad because the pay-off is worth it. Any way you slice it, keeping outdoor wood stained, painted or sealed is a lot of work, so you might as well get the most mileage from the time you spend on your hands and knees. And it all begins with an obscure bit of information about lumber.
The first thing to understand is that new wood is a poor candidate for finishing as it comes from the lumberyard. And the reason is something called ‘mill glaze’.
Every piece of construction lumber in the world is prepared using a two-step process. First comes the saw blade that slices round logs into rough lumber. Next is the planer. It uses high-speed revolving knives to shave the surface while smoothening it, bringing the wood down to standard dimensions. And while this is excellent and necessary, planing also imparts a slightly burnished surface to the wood, preventing full absorption of film forming finishes. This is the problem. When paints, stains and tinted varnishes can’t get a good foothold into the pores of the wood, they peel way too soon. This is the danger, but it can be avoided.
The trick is removing the mill glaze before finishing begins, and there are two ways to do it. The first and easiest is to slosh some mill glaze remover onto the wood, let it sit as directed, then rinse it off, ideally with a pressure washer.
While this procedure does remove some of the burnished surface that inhibits finish absorption, there’s a second step that makes wood even thirstier. If you have the time and inclination, consider sanding your outdoor wood when it’s fully dried after the chemical mill glaze treatment. This job can be simply tiring or absolutely unbearable, depending on the sander you’ve got.
Give yourself every chance for success and use a 5 or 6-inch diameter random orbit sander with a 60- or 80-grit disk installed. Forget the little quarter-sheet finishing sanders (they’re too weak) or the hand-held belt sanders (they’re too unwieldy for this job). Sand, vacuum, then finish knowing you’ll get the best possible mileage from the coating you apply. Today’s top products last as long as 36 months on a deck, the worst will need maintenance in a year.
Do you have weathered, thirsty outdoor wood you’d like to finish? You certainly don’t have a mill glaze problem, but there is something else you need to consider. When wood goes gray, it means that surface fibres are being broken down by sunlight and water. And while these fibres are very absorbent, they’re also weakly attached to the underlying wood. That’s why gray wood needs to be sanded, too. It removes loose surface fibres that would otherwise detach from the wood underneath, letting the finish go with it.
Maintaining paint or stain on outdoor wood involves work. That’s part of the price you pay for this material, but it needn’t turn you sour. Tackle the prep work right and you’ll have plenty of time to enjoy the beauty of your outdoor wood, too. |
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