Teak wood contains natural oils which help prevent it from rotting or deteriorating in a natural environment. Unfortunately, these oils also cause teak to turn gray or black due to mold and mildew feeding upon the oil.
On this page, we describe how to clean and protect teak. We also describe teak treatments such as oil, varnishes and sealers.
There really isn't any secret to cleaning teak except that it requires some elbow grease (nobody has figured out how to package that yet).
There are basically two reasons to clean teak. First, you want to remove the black and/or gray color (actually mold & mildew) from the wood and get a more natural look. Second, you need to kill all the mold and mildew spores present so they won't continue to eat the teak oil and discolor the wood.
How NOT to clean teak...
With a powerwasher - Powerwashers just blast away dirt and expose raw wood. Not only is this rough on your teak, it also doesn't kill the mold and mildew spores in the wood.
With household bleach - Bleach is not strong enough to kill the mold and mildew spores in the wood.
With tri-sodium phosphate (TSP) - As with bleach (see above), TSP isn't going to kill the micro-organisms living in the wood.
The right way to clean teak...
To clean teak, all you really need is a bottle of "teak cleaner". These products are formulated to kill the mold and mildew and restore the natural wood color. There are generally two types of teak cleaners, one-part and two-part cleaners.
One-part cleaners come in a single bottle and use a mild chemical to clean the wood. We prefer one-part cleaners because they are much gentler. Because they are relatively mild, you need to work the cleaner into the wood with a bristle brush and let it sit for 5-15 minutes before rinsing it off. While rinsing the wood, use bronze wool to rub the surface (in the direction of the wood grain). This opens up the pores of the wood to remove all of the cleaner ensure that the wood is as clean as possible.
Two-part cleaners come in two bottles and typically consist of a harsh acid and a neutralizer. The first part (the acid) chemically cleans the wood, killing the mold and mildew spores and removing the black and gray color. This step works faster and requires less work than for one-part cleaners, but the harsh acid also raises the wood grain (making your wood rougher). The second part is a neutralizer which counteracts the acid, allowing you to rinse off the teak safely. We generally discourage the use of two-part cleaners because of the damage they can do to your teak and the environment.
Treating and Protecting Teak
After your teak is clean and dry, it's time to apply something to the wood to give it a nice appearance that (hopefully) will last. Teak oils penetrate into the wood and replenish the oil supply while teak sealers coat the wood and provide a barrier to the outside environment. These treatments have different advantages and disadvantages, so let's look at them in more detail.
Teak has traditionally been treated using organic oils, although an replacement for teak oil is available that overcomes many of the problems with organics. The organic oils replenish the oil removed from the wood by the environment and the cleaning process, restoring a nice satiny finish to the wood.However, remember why the teak was cleaned in the first place. Mold and mildew spores were feeding upon the teak oil and turning the surface black or gray. When you oil teak, you are also providing more food for the mold and mildew. Consequently, you have to re-clean and re-coat your teak several times a season (on average).
Teak sealers try to seal the wood surface from the environment in order to maintain the appearance of the wood and (sometimes) provide a glossy finish. The traditional material for sealing teak has been varnish or polyurethanes. The main drawback with sealers is that they will eventually break down and begin to flake off. The sealer must then be sanded off (lots of work!). While sealers may look good initially, they can also require a lot of maintenance and even more work to remove them.