Remove dirt and buildup. Wipe down the table with a cloth or bristled brush to remove dirt, dried-on leaves or other debris. Using a bristled brush will help remove small particles such as mildew lodged in the wood grain and joints for a smoother finished look.
Scrub the table with a teak cleaning solvent or a mixture of 2 parts laundry detergent with bleach to 1 part water. Scrub in the direction of the wood grain to remove bacteria and mildew. Rinse the table with water to determine if you need to clean it another time to remove any stubborn dirt or mildew. Wear rubber gloves during this step to ensure you don't harm your skin.
Allow the teak table to dry completely, and protect the table with teak oil or sealant in your choice of finishes. You can leave the gray finish, or bring the teak back to its original brown wood grain. Apply the teak oil or sealant with your paint brush or soft clean cloth as directed on the package.