There are a number of products available today that contain pigments, ultraviolet light blockers or absorbers, mildewcide, and moisture protection to seal and protect in one step. I recommend a visit to a local marine store as teak is used on boats and they can be an excellent source of information on teak sealers. As mentioned above, teak is a beautiful wood and with proper care can look great for years.
Things You Will Need
Teak sealer, Scotch Brite Pad or brass wool, Teak clear coat, Liquid Ivory soap or another mild neutral ph detergent, Sponge, Soft bristle brush, Soft cloths, Nylon, polyester or foam paint brush, 320 grit sandpaper, Drop cloth to protect area under furniture during cleaning and sealing, If the mildew stains are persistent, a mixture of chlorine bleach or ammonia in weak solutions with water or mildew products such as Tilex or X-14. NEVER MIX BLEACH AND AMMONIA TOGETHER.
If you are sealing new teak I recommend allowing it to sit in the sun for about a week to open up the wood grain. At this point a cleaning with a mild detergent and sponge should be all that is needed prior to applying the teak sealant. Allow the wood to dry completely, usually overnight.
Brush on the teak sealer with a paint brush or spray on. Then rub the sealant in with a soft cloth. Be sure to coat all areas of the furniture including the top, bottom, sides and between all slats. Allow the first coat to dry completely before putting on a second coat. Areas such as table tops that are susceptible to stains from foods, drinks or other items that can penetrate the sealer should be sealed with a teak clear coat. Keep in mind that teak has natural oils that come to the surface that will cause varnish, polyurethane and water sealers to bubble, chip and peel. Therefore, always use a "teak" clear coat.
If your teak patio furniture has already started to turn silver-gray and you want to return it to its original golden brown or honey color, you will first have to clean the wood prior to applying the teak sealant. Begin by cleaning the wood as in step one above. If mildew is present try to clean with a soft bristle brush and liquid Ivory soap. If the mildew stains are persistent, a mixture of chlorine bleach or ammonia in weak solutions with water or mildew products such as Tilex or X-14 can be used. Whenever using bleach or ammonia to clean the wood always rinse quickly with plenty of water to avoid the wood turning white. NEVER MIX BLEACH AND AMMONIA TOGETHER. There are also two part teak cleaners available that use a caustic soda and an acid to produce excellent results.
After cleaning, allow the wood to dry completely. Lightly sand the surface of the wood with 320 grit sandpaper. Remember to always sand in the direction of the wood grain. Use a clean dry cloth to clean any sanding dust. The wood is now ready to re-seal. Follow Step Two above and you are ready to enjoy your furniture again.
Caring for teak patio furniture can range from doing nothing and allowing the sun to age the wood naturally to a silver gray color to treating and sealing the wood every 6 to 12 months depending on the environmental conditions where you live.
Tips & Warnings
To test to see if your teak furniture needs re-sealing, simply lightly spray water onto the surface. If the water beads up then the wood does not need to be re-sealed.
Never use steel wool to clean teak as the fibers left behind will cause rust stains in the wood.
Do not use harsh detergents or pressure washing to clean teak furniture because they can damage the wood.
Whenever working with tools and or chemicals, safety glasses are recommended. Masks and gloves are also recommended to be worn when working with some types of wood cleaners.
NEVER MIX BLEACH AND AMMONIA TOGETHER