The pre-staining stage of the project is a crucial one. It prepares your canvas for what will doubtless be wood-deck work of art once you're done. The typical process looks like this.
We'll call it cleaning, but it's not your simple soap-and-water job. This initial step, which of course has multiple components, aims to remove any flaws, mildew and contaminants that can ruin (or at least deter from) the final look of your project.
Cleaning typically begins with sanding away imperfections, repairing lightly cracked or loose boards, and replacing heavily damaged or decayed ones.
Next comes spraying or wiping a wood-cleaning product onto the entire deck, one small section at a time because you want it to still be wet when you work it in with a stiff-bristled brush. You'll leave it for at least 10 minutes, and then rinse with a regular garden hose or pressure cleaner (on a low setting).
All clean? Let it dry thoroughly. This could take a couple of days.
If your deck has been stained previously, and you're adjusting the color, you'll need to remove the old before applying the new or else the new finish won't "take" the way you want it to. This is also your chance to eliminate any old-finish flakes or stray wood fibers.
Wood strippers are intense products, so remember to wear your protective gear, including eye goggles, mask and gloves.
Brush on a heavy layer, and let it sit until the old finish starts to come up (you'll see it bubble). This will usually take about a half hour, after which you'll begin scraping it off with a flat-edged tool, like a putty knife. Use an old towel or T-shirt to wipe finished spots as you go. Then rinse well.
While not strictly necessary, wood brightener is a great way to bring out the original look of the wood you loved so much you built a deck with it. Cedar and redwood benefit from a brightening product especially, but it can make any wood look fresher and has the added benefit of removing rust and mildew.
Some products want you to apply when the wood is wet, while others want it dry. So be sure to check the manufacturer's instructions.
Wipe (or spray or brush -- read the instructions) an even layer onto the boards and let it sit for about 15 minutes, keeping it constantly wet with a spray bottle of water or a hose with mist setting. Then, rise well, and let it dry.
Seriously, let it dry. You're going to be staining next, and you want to apply stain only to completely dry wood. If it takes a day or two, wait it out.
Clean deck? Check. Smooth, stripped, gleaming boards? Check. Totally dry? Check.
Now, it's time to stain.