Cedar is a popular wood for all sorts of outdoor building projects. Wood siding, fences, trellises and other garden implements are commonly constructed from the wood in large part because of the elegant way in which it ages. Additionally, cedar is naturally infused with protective compounds that allow the wood to perform wondrously in the elements. From time to time, though, the wood can be stained by various conditions, including water. Removing these unsightly blemishes can be easy if you follow the right steps.
Qualities of Cedar
Cedar wood is unparalleled in the outdoor environment for the warmth and natural look it creates. Few woods are capable of blending into a scenic environment the way cedar can. Likewise, few woods are able to withstand the elements with the same measure of grace that cedar does. Many homeowners forgo the process of staining or painting cedar, opting instead for that naturally weathered look that is sought after by purists and gardeners with a penchant for the nostalgic.
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While the aesthetic is remarkable, some individuals with outdoor structures made from cedar forget that a few basic preventive measures should always be performed to protect the wood from stains and blemishes, even if stains and paints are not going to be used. Tim Carter, of Askthebuilder.com, a homeowner resource for home maintenance, suggests a simple application of oil-based water sealant to new cedar wood before installation or building. This effectively eliminates many of the potential stains that can occur during the lifetime of your structure, particularly water stains.
Water stains are one of the hardest to remove from cedar wood. The Western Red Cedar Lumber Association (WRCLA) points out that water stains are typically a combination of extractive bleed and mildew. Mildew is easily dealt with by using a pressure sprayer and applying a mildewcide to the affected areas. Extractive bleed, however, is much more complicated. This type of stain occurs when water penetrates into the wood. The naturally occurring chemical extracts that make cedar so unique also happen to be highly water soluble. As outside forces such as wind, sun and warm weather draw the water back out from the interior of the wood, the extracts emerge with it. The water then evaporates from the surface, oftentimes leaving a dark brown stain, which is simply the concentration of extracts that were once spread out within the wood.
Water Stain Removal
To remove stains that have resulted from extractive bleed, the WRCLA suggests a dilution of oxalic acid. Tim Carter expounds on this, advising a pre-wash of "One cup of trisodium phosphate, one cup of bleach and one gallon of water, and wash the siding with this solution." Then follow with the oxalic acid. Carter recommends a dilution of four ounces oxalic acid crystals to one gallon of warm water. When using the oxalic acid treatment, be sure to wear protective gear such as goggles, gloves, a long-sleeved shirt and long pants. Oxalic acid, like many acids, is caustic even when diluted and should be handled carefully. These simple precautions will enable you to safely eliminate the extractive bleed stains. Once finished, you should save yourself the trouble of repeat treatments by applying an oil-based water repellent to the wood. This will prevent water from ever creeping inside, where it can dissolve the natural cedar extracts.