5 year old furniture with new TeakGuard finish applied
Congratulations, on your purchase of a set of teak wood furniture. If you care for it properly it will be part of the estate that your children will be fighting over. Teak furniture even in the far north and deep south will stand up to the worst mother nature can throw at it save the occasional hurricane or tornado.
Weather you leave your furniture completely unfinished, oil it, seal it or use a breathable finish, consistent care will make you furniture last for at least one life time. The difference between the various finishing techniques is how much labor is involved in maintaining the finish.
By the way, any time you see teak or teak wood, it includes woods like ipe, iron wood, rose wood, and all the hard oily tropical woods as well as cedar and cypress .
Unfinished Teak
If you choose the unfinished look for your teak, it will turn gray in several months. If that was all that happened life would be very good in deed. However, that is not all that happens. Mold will grow on both the grayed teak resin that migrated out of the wood and on the wood itself. Often moss will grow where dirt accumulates. The net result is that the surface of your teak will soon require cleaning and the surface of the wood will begin to become very ruddy or checked. This is primarily due to the action of the mold and moss eating away the softer parts of the wood while leaving the harder wood (year rings).
Oiling your Teak
Coating teak with tung oil or lemon oil certainly makes it look good after cleaning the wood with detergent, TSP or oxalic acid. It protects the wood for 1 or 2 months and then needs to be washed off and replaced with fresh oil. Further oil actually promotes the growth of mold and though the mold feeds primarily on the oil itself the wood is often involved.
Insolently, teak wood is so dense and filled with resin that it can only absorb a very small amount of cleaner, finish or oil, the rest just lays on top of the wood.
Using Sealing finishes
Sealing finishes like varnish, urethane, epoxies, and sealing polymers do a really good job of sealing out all the stuff that is likely to damage your teak. Some are better than others based on the exact mixture of UV reflective or absorber products included in the product. These finishes will normally last one or two years, though many can not tolerate the hot sun or cold winters for more than a few months. The root issues that control the life of a sealing finish is:
- How fast the finish becomes hard and brittle and
- How much water was trapped between the surface of the wood and the finish
The trapped water vaporizes when the sun shines on it causing a very tiny gas pocket to form on top of the teak and under the sealer. Each time the sun goes behind a cloud the pocket disappears because the water vapor condenses back into water. This cycle of heating and cooling can happen many times a day. Each time each gas pocket gets slightly larger. Eventually, adjacent gas pockets will combine into one pocket and eventually become a blister that will ultimately fail along the edge and fall off. These blisters are not repairable and require that the finish in the entire area be removed and reapplied.
Finishing with a breathable finish
There are a very few breathable (gas permeable) finishes available. All are made from water soluble acrylic polymers. Being water based has its own challenges. The number and color of UV reflective additives is very limited. The number of color additives that will not leach out is also very limited. The polymers ability to bond with other finishes and non wood materials is very limited.
These short comings demand that the wood being coated be free from wax/teak resin and any previous finish except water soluble acrylic polymers. This can be a tall order for boaters with deep (but necessary) checking in their decking, swim steps and platforms.
Cleaning off old finishes using MEK stripes really work pretty well but they smell really bad and can damage your gel-coat. Using special degreaseers cleaners to remove the teak resin completes the cleaning. Fortunately, this cleaning process only has to be done once because refreshing the finish can be done by simply washing the finish with soap/detergent and water, and applying a fresh coat or two of polymer.
There is one issue with breathable finishes that should not be overlooked or under estimated. Breathable finishes are a double edged sword. They breath both directions. When they become wet from rain, cleaning or use (as in boat) the finish darkens until the water evaporates. This is not a problem until you mix the water wine, or colored food in which case the finish will acquire the color of the wine or food. This problem can be easily avoided with furniture by occasionally waxing the surface with pure carnuba wax. This wax must be removed with a mixture of water, detergent and ammonia before re-coating the surface with additional polymer.
Removing stains is possible by removing (sanding away) just the stained polymer finish and a little of the surrounding area, re-cleaning the wood and re-coating the area with polymer until it matches the surrounding area.
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