Got Milk?

17 August 2009 By Scot Henry, WoodTech Marine

Just imagine, you’re an owner who ordered a brand new, custom-built yacht. You wait two years in anticipation for your new baby. But shortly after you take delivery and sit down to enjoy the yacht’s interior, you start to notice creamy white patches spoiling the beautiful color and richness of the woodwork….

If your yacht was purchased in the last five to 10 years, then you may also have“gotten milk.” To help understand the present problem, we need to step back a few years and see how we got into this mess in the first place.

When I started in the industry back in the early ’90s, there were only two choices for a finisher to spray on the interior woodwork: nitrocellulose lacquer or pre-catalyzed lacquer. Now, with all the new products out there such as acrylic lacquers, conversion varnish, two-component poly-urethanes, polyesters and waterborne clears, choosing the best finish is like trying to choose the best dish at an all-you-can-eat buffet. If you are not a professional in the interior finishing industry, all the choices can be confusing.

Let’s look specifically at polyester, which I feel may be to blame for the current “blushing” or “milky” epidemic affecting the yachting industry today. Polyester is used by most of the major yacht builders during the wood-sealing process due to its quick-dry and easy-to-sand properties. Polyester also is known for its superior high-build characteristics, which mean fewer coats needed and therefore, quicker results.

So what’s the problem?

One possible cause of the “milky” discoloration is what happens in the spray cup during the final moments of the application process. The internal heat from the catalyst causes thousands of little bubbles to appear, which are later sprayed onto the woodwork. This is usually not noticeable at first, but later appears and worsens with sun exposure.

The other possible cause is polyester’s ability to absorb moisture. Just as in shirts, where it is blended with cotton to help keep people dry, it's a moisture-absorber. Most of the “milky” problems I’ve found have been around A/C units and high-moisture areas. Normally, the areas with the most “blushing” are wall panels and doors with unfinished end or back panels.

There are two ways to prevent this problem from happening. My first recommendation is to seal the back and ends of all the doors and wood panels. The other is to try using a different product other than polyester to seal the wood in the first place. Products like lacquer may take a little longer to build up but, they may save you time in the end.

Even in our quest for the hardest, most durable, chemically resistant wonder product, we realize that nothing is perfect. Everything has it pros and cons. In my opinion, polyester has way too many cons. Fastest and easiest is not always the best.

Does your yacht “got milk?”