If left untreated, teak will change over time from a warm honey-colored woodgrain to an elegant silver-grey patina. This transition is merely aesthetic and does affect the integrity of the hardwood or its ability to resist the elements outdoors. If you want to restore teak to its original coloration, you can but it takes a little effort.
Clean the wood - Remove surface grime and dirt with soap and warm water
Scour it - Using a scrub brush or scouring pad with a gentle cleanser, lightly scour the teak across the grain
Rinse the teak - Use running water to clear the wood of any loose debris and soapy residue
Remove stubborn stains - If needed, use a commercial teak cleaner with a strong abrasive and mild acid to get rid of deep stains
Sand the surface - Use medium to fine sandpaper to smooth out any texture imperfections
Apply teak oil - Spread teak oil with a soft rag in the direction of the woodgrain
Apply sealant - Apply one thin coat of sealer and allow it to dry before applying a second