By Paul Bianchina
A well-built wooden deck, fence, gazebo or other outdoor construction project can enhance the appearance and the value of any home and often represents a pretty sizeable financial investment as well. But all too often, these structures are simply left to weather away with little or no thought to their upkeep. So if the wood that's gracing your backyard oasis is starting to seem more of an eyesore than an asset, it may be time to consider some cleaning.
Fortunately, the new generation of wood strippers and cleaners that are now on the market have made this a far less formidable task than in years past. With the right product and a weekend's worth of effort, you can make a huge difference in even the most gray and weathered deck.
First, you need to determine where 
to start. If your deck - or any other outdoor wood - has been previously painted or stained, you'll want to begin the process with a stripper that's formulated specifically for this application. Some products, such as Wolman's DeckStrip, will strip both oil and latex paints and stains and will also cling to vertical surfaces to simplify application. It's premixed and can be applied with a brush, roller or garden sprayer.
If your deck does not have an old finish on it but has just weathered over time, one of the many specially formulated wood cleaners will have it looking almost new in no time.
In years past, most wood cleaners resorted to the use of chlorine bleach, which is a difficult - and in some instances very dangerous - product to work with. Bleach can be very hard on the wood, lifting and damaging wood fibers and leaving the wood unnaturally white in some areas. It can be equally hard on surrounding lawn and plants.
Most of today's cleaners are not chlorine-based, making them both safer and easier to apply. For example, Redwood and Cedar Deck and Siding Brightener/Rejuvenator, another Wolman product, comes in powder form and is mixed with water. It is applied by brush, roller or garden sprayer and will remove dirt, mildew and some types of staining, as well as tannin stains.
Wolman suggests working with about a 10-foot by 10-foot area at one time. Apply enough of the cleaning solution to keep the area wet, and allow it to sit on the wood for about five to ten minutes. You can then work over the wood surface with a stiff broom to further dislodge dirt, then rinse it off with a hose. You'll also want to rinse off any adjacent plants. Finally, allow the wood to dry for at least 24 hours before the application of any finishes or preservatives.
With deck cleaners of this type, you shouldn't have to resort to a pressure washer in order to get good results - let the cleaner and the broom do the work. However, if you do choose to rinse with a pressure washer, be sure that you select a wide, soft-spray tip that will rinse the surface without digging into it and possibly damaging the wood.
If your deck is made with pressure-treated wood instead of cedar or redwood, look for a cleaner that is formulated specifically for that material. Most products designed for pressure-treated wood utilize sodium percarbonate as the active ingredient, which is the same ingredient that's used in many of today's color-safe laundry bleaches. Sodium percarbonate-based cleaners - which will work on other types of woods as well - are safe when handled according to package instructions. They are very fast and effective cleaners that will remove dirt, mildew and weathered gray residue, returning to the wood much of its original color and brightness.
Another common problem with cedar, redwood and certain other species is a natural resin in the wood called tannin. Tannins, which are water-soluble and a reddish-brown in color, can migrate to the surface of the wood and be deposited there, leaving dark brown discolorations. Tannins can also react with the metal in the fasteners that secure the deck boards, resulting in dark, blue-black stains that can really mar the appearance of the wood.
For tannin stains, look for a clean that is oxalic acid-based. Oxalic acid will work with the tannin and iron stains to turn them virtually colorless, making it a great cleaner for cedar or redwood. Oxalic acid, however, will not clean mildew and some other types of stains, so if tannin is a problem look for a cleaner that is formulated for all types of cleaning - tannin, dirt, and mildew - or use a general-purpose cleaner first, followed by an oxalic acid cleaner specifically for the tannin.
With any cleaner, always follow the manufacturer's specific instructions for application, cleaning and protective clothing.
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