Stop feeding the fungus: Traditional oils trap dirt and encourage mildew (right). Modern water-based protectors block UV rays while letting the wood breathe (left). Do not use traditional "Teak Oil" on outdoor furniture.  Paradoxically, most "Teak Oils" are made from linseed or tung oil, which trap moisture and encourage black mildew spots. To maintain the golden colour, use a Water-Based Teak Protector . To achieve the classic silver-grey patina, simply leave the wood untrea