Wood- and Barrel-Aged Sour Beers are very light to black. Any lager, ale or hybrid beers, either in a traditional style or unique experimental beers, can be aged for a period of time in a wooden barrel or in contact with wood, and, develop bacterial induced natural acidity. These beers are aged with the intention of introducing the micro flora present in the wood. Sometimes wood aging is intended to impart the particularly unique character of the wood and/or what has previously been in the barrel; but, wood aged is not necessarily synonymous with imparting wood-flavors. New wood character can be characterized as a complex blend of vanillin and/or other unique wood character. Used sherry, rum, bourbon, scotch, port, wine and other barrels are often used, imparting complexity and uniqueness to beer. These wood-derived flavors, if present in this style, can be very low in character and barely perceived or evident or assertive as wood-derived flavors. Any degree of wood-derived flavors should be in balance with other beer character. Usually bacteria and "wild" yeasts fermentation contributes complex esters and results in dry to very dry beers. Ultimately a balance of flavor, aroma and mouthfeel are sought with the marriage of acidity, complex esters, and new beer with wood and/or barrel flavors. Wood-Aged Beers may or may not have Brettanomyces character. Body is variable with style. Fruit and herb/spiced versions may take on the hue, flavors and aromas of added ingredients. Brewers when entering this category should specify type of barrel used and any other special treatment or ingredients used. Competition managers may create style subcategories to differentiate between high alcohol and low alcohol beers and very dark and lighter colored beer as well as for fruit beers and non-fruit beers. Competitions may develop guidelines requesting brewers to specify what kind of wood (new or used oak, other wood varieties). The brewer may be asked to explain the special nature (wood used, base beer style(s), special treatment or ingredients and achieved character) of the beer.