Every year it distresses me to see my fellow sailors painstaking sand their boats teak to bare wood, carefully tape the deck, then apply two or three coats of their favorite teak coating, while sometimes ignoring the manufacturers explicate instructions. A year or two later, all their hard work vanishes, leaving behind the dismal residue of another failed coating job.
If you want your brightwork to last more than one or two seasons, it’s important to apply at least six coats of finish because the suns UV rays will burn away one coat of finish every three to six months. While the sun is destroying the top coat, it’s also attacking the underlying one.
It is also critical to roughen the surface by sanding between coats. The reason for this is simple – subsequent coats do not chemically bond to each other. Additional coats must mechanically adhere to the previous one. A coatings molecules need to grab onto something to stick together to prevent peeling away. The tiny scratches made by lightly sanding the existing coat allow the current coat to adhere to the previous coat. Without these tiny scuff marks, you’re literally coating polished glass that has no adhesive properties. You can imagine how long that will last.
Additionally, you should vacuum clean the sanding dust and then wipe off any sanding residue with the solvent that the manufacturer recommends. This is an important step because the sanding dust will diminish the adhesive qualities of the next coat. If you don’t do this, you’re applying the finish over a thin layer of non-adhering microscopic dust.
If you use a varnish-type coating (which is the only type I use), here is what works for me:
1 – Start by sanding the wood bare, then vacuum, and then wipe the surface clean with acetone to remove the teaks natural oil.
2 – Apply at least six coats of finish – thin the first two coats to fill the woods grain.
3 – Lightly sand with 220 grit paper between coats.
4 – Vacuum and wipe off the sanding residue with solvent before applying the next coat.
If six coats seem too time-consuming, think about all the time it takes to sand the wood bare and then tape the deck. Of the total time spent finishing teak, applying six coats is a very small portion of the task. With a little luck from the weather gods, you can apply six coats over three days – one in the morning and one in the late afternoon.
UV is the enemy of coatings longevity; therefore, you should consider one more step. After the coating totally cures (about 45 days), apply 3M – Marine Protective Liquid Wax with UV protection (3M product code # 09026). I apply that wax twice every season. It’s simple and fast – wipe it on – wait five minutes – wipe it off. However, don’t use that product unless you’re sure the grain is filled; otherwise, it will leave a white residue in the unfilled grain. It’s wise to test a small section before applying this product.
Following these procedures will give you a good chance of getting about five years from your coating work.