Why is my teak deck turning white?

A teak deck turning white is almost always caused by a buildup of dried salt crystals from sea water washdowns or calcium deposits from hard marina tap water. It can also occur if you have recently used an aggressive two-part chemical cleaner containing oxalic acid, which severely bleaches the wood fibres if left on too long.

Salt and Hard Water Deposits

Sea water contains roughly 35 grams of dissolved salt per litre. When you wash the deck with sea water and let the sun bake it dry, the water evaporates. This leaves microscopic salt crystals trapped in the open grain of the teak. Over several weeks of dry weather, this buildup creates a visible white haze. Sea water is traditionally used to keep teak damp and swollen. Relying on it entirely during hot summers leads directly to this salt frosting.

The culprit might instead be your marina fresh water supply. Many coastal marinas pump exceptionally hard water. When you hose down the boat, calcium carbonate remains after drying. Just like the limescale around a domestic bathroom tap, this calcium forms a white bloom on the wood. Teak is naturally porous. It holds onto these minerals stubbornly, making the deck look prematurely aged.

The Two-Part Cleaner Trap

If your deck has turned a stark white rather than a greyish hue, suspect chemical bleaching. Many owners try to restore silver teak using strong two-part chemical cleaners, such as Snappy Teak-Nu or Star brite Premium Restorer.

Part A of these kits is typically a strong alkaline like sodium hydroxide. This strips away dirt, old teak oil and grease. Part B is an acid, usually oxalic or phosphoric acid, designed to neutralise the alkaline and brighten the wood. If Part B is mixed too strongly, left on the deck for more than a few minutes or not rinsed away completely, it destroys the natural lignin and pigments. Oxalic acid is a potent bleaching agent. Misuse leaves your teak looking like white pine and degrades polysulfide caulking.

Diagnosing the White Bloom

Finding the cause dictates the fix. You can diagnose the issue in seconds on board:

• The taste test: Rub a clean finger heavily on the white patch and touch it to your tongue. If it tastes salty, you have sea salt buildup. Flush the deck thoroughly with fresh water on a rainy day. Use a sponge to lift the crystals out of the grain.
• The limescale check: If the deck only turns white after hosing it down in the marina, you have hard water. Wash the deck with a mild acidic solution to dissolve the calcium. Mix one part cheap white vinegar with four parts fresh water. Wipe it over the deck with a sponge and rinse it off completely after five minutes. This will not harm modern marine caulking like Sikaflex 290 DC or TDS SIS440.
• The chemical check: If the wood is bleached from oxalic acid, you cannot wash the white away. You must wait for the sun to naturally weather the surface back to a silver-grey. This process usually takes a few months of exposure.