Tuesday, March 20, 2012

Stripping Bottom Paint

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. 

"Paint sick"

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.

Tom and Garrett Eisele rolled two coats of linseed oil on the hull, and left it for a day, so the oil could fully penetrate the paint. They lay plastic down under the boat to collect all of the scrapings so they do not end up in the soil around the boatyard.

The following day, they took torches and sharp scrapers to the hull. Here’s what it looked like:

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. 

Tom Kiley
Garrett wielding the blow torch.
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.

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At July 6, 2012 at 11:39 AM , Blogger Sam Ward said...

I might have to give this a go. I have a 60ft trawler to single-handedly strip. Did you use boiled or raw linseed oil for this?

At April 28, 2017 at 9:54 AM , Blogger Tom Crowley Senior said...

We use organic raw linseed oil, lay it on thick with one coat if inside or two outside, the next day we use dueling HEAT GUNS (my wife and I) and very sharp ALLWAY scrapers. Result is clean, bare wood, with NO burnmarks or scary flames...1958 Wooden Lobsterboat -

At July 19, 2017 at 2:55 AM , Blogger seravina danniella said...

Thank you for sharing this interesting and informative article, painting with airless spray gun will be faster and more interesting!

Airless Spray

At September 20, 2017 at 4:16 AM , Blogger seravina danniella said...

Thank you for sharing this interesting and informative article, painting with airless spray gun will be faster and more interesting!

Spray Gun

At February 19, 2019 at 3:15 AM , Blogger StevenHWicker said...

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At March 25, 2020 at 3:40 AM , Blogger romanirestoration said...

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stripping wood


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Location: Rockport, Maine, United States

Rockport Marine is a group of talented craftspeople who design, build and restore wooden yachts with unparalleled expertise.