Stripping Bottom Paint

video, photographs and text by Maria Simpson for Rockport Marine

Everyone knows that anti-fouling bottom paint is essential for the performance of a yacht. These paints contain heavy metals, biocides or photo-activated materials that discourage marine growth.

Bottom paint is always a hot topic among boat owners and boatyard workers alike. Recent environmental regulations concerning bottom paint have changed the way we do things at Rockport Marine. In 2010, we installed a catch basin to collect bottom wash water, which is filtered and then discharged into the town septic. This protects the delicate, intertidal zone in Rockport Harbor from the concentrated heavy metals found in the waste water discharged after a  boat bottom is washed in the fall. Although expensive to install, it is important that our coast line be protected by tighter regulations. Regulations such as these are  also driving paint companies to come up with more environmentally friendly formulas for their bottom paints.

Over time, bottom paint can build up on the bottom of a boat and the paint will no long adhere to the substrate. Billy, long time painter at the yard, calls a boat with this condition “paint sick.” Even ablative paints can build up too much, even though they are designed to slough off as a boat moves through the water over the course of a season. When the paint gets thick and starts to flake off in large patches, exposing bare wood, we know it is time to strip all the paint off the bottom of the boat and start fresh.

Stripping the bottom of a wooden boat, of any boat, is an awful job. The paint crew has tried many techniques and methods to find the quickest and easiest way to strip a bottom. We have used scrapers with and without blow torches, and we have recently been using a product called 5F5, a very effective paint stripper. The drawback of the 5F5 is that it is particularly toxic stuff, requiring a respirator, goggles, and a protective suit. It turns the existing paint into goo, which not only drips down your tyvex-clad arms, it is difficult to contain and collect for disposal, and can ruin jack stands and ladders. 5F5 is expensive. But, it reduces our labor drastically and that has seemed to us a good trade-off.

Recently, Tom Kiley suggested a new way of stripping bottom paint with linseed oil and a blow torch. Aaron, the paint foreman, was skeptical, but Tom was adamant that he wanted to give the new method a try. Aaron agreed to help him.

To our delight, the paint came off easily, and with minimal scorching to the wood underneath.

The way Tom describes it, the fire from the torch ignites the linseed oil, which blows the paint off the hull. Thus, the linseed oil burns instead of the wood, which explains why we saw so little scorching. The process went quickly, as quickly as the 5F5, in our estimation. It also was cleaner and more pleasant to perform. One caution to anyone trying this method would be to treat the linseed oil very carefully, making sure any soiled rags are in a fire proof bin at night, and storing the container in a fire proof locker. Linseed oil can spontaneously combust, and therefore must be handled with extreme caution.

Another method for stripping bottom paint is to blast the hull with sodium bicarbonate or walnut shells; both substances can be used to remove paint without damaging the surface below. We have yet to try this technique; it is most easily carried out by a subcontractor because of the set-up and clean-up involved. We look forward to comparing that method to others we use.