Sand the teak furniture with fine-grain sandpaper.
Mix 2 cups of household ammonia with 1 capful of laundry detergent after donning a pair of rubber gloves.
Apply the cleaning solution to the teak furniture, using a scrub brush to gently clean the furniture while working in straight, horizontal lines from top to bottom. Dispose any unused cleaning solution after you have cleaned the entire piece of furniture.
Rinse off the teak furniture with a hose and allow it to dry completely, preferably in the sun, for at least three days.
Pour teak oil onto a clean, lint-free rag after donning rubber gloves and apply the oil to the teak furniture from top to bottom. Allow the furniture to dry overnight before using.