Bottom Paint Stripping
Is removing antifouling with a heat gun a viable option?
My husband, Ken was in the fiberglass business for over 25 years. We intend to take off all of our boat’s bottom paint (about 12 coats total) down to gelcoat, epoxy the surface, and then apply new paint during our next haulout.
Getting the old paint off by sanding is a horrible job, and sodablasting is not an option where we intend to haul in Panama. Chemical strippers are expensive and also require wearing a lot of personal protection. So Ken has decided to use a heat gun to heat up the bottom paint and then scrape it off as he is quite familiar with gelcoats and the heat they can withstand. We are also aware that the heat will drive toxic fumes off the surface, but that can be worked around by working upwind, and those fumes will be a lot less hazardous than dust from sanding.
As an experiment, he applied bottom paint to a fiberglass panel, allowed it to dry two days, then warmed the surface, and easily scraped off the paint. It was easy to peel it off the scraper and safely discard.
Do you have any information/experience on removing antifouling with heat?
Joan & Ken Church
Dancing Walrus, 2005 Privilege
Although we’ve tackled our share of varnish with a heat gun and scraper, we’ve never used them to strip bottom paint. The obvious concerns would be marring the gelcoat and the noxious fumes created by heating paint solvents and active ingredients. Our first choice for removing antifouling would be sodablasting (PS, October 2011), but as that’s not an option for you, we’d consider chemical stripping (PS, April 2008 and March 2009), wet-sanding, or vacuum sanding.
As we’ve discussed in past articles, each method has its inherent pros and cons for a DIYer, and all involve contact with some pretty evil toxins, so wearing a proper respirator, Tyvek suit, gloves, and eye protection are musts. Simply “working upwind” from the dust or fumes won’t cut it—especially when you’re under the boat and heating up the old paint. Also, be mindful of others in the work area and stage the project so your yard neighbors won’t be inhaling the poisonous fumes as they are released or breathing the dust.
PS got mixed feedback from antifouling makers regarding heat stripping bottom paint. According to Interlux’s Jim Seidel, it is not recommended because of the fumes that can be released and because of the risk of melting gelcoat. He suggested media-blasting or using a vacuum sander with a HEPA filter as safer methods.
However, Kop-Coat/Pettit’s Frank Winkelman said that he had used a heat gun and scraper to reclaim fiberglass test panels but that he had never known anyone to use it to strip an entire hull. “The labor involved is about the same as using a paint stripper and probably slightly less than sanding,” Winkelman said. He added that the type of antifouling will determine how easily it comes off: Hard paints will be easier to heat and strip as ablatives tend to gum up on a scraper. He also echoed concerns about toxic fumes coming off heated surfaces as did Sea Hawk Finishes’ Jason Revie, who said the safest bet is an environmentally friendly paint stripper.
In our opinion, only the most deft of heat-gun handlers should consider using one to strip antifouling from gelcoat—resin damage occurs at relatively low temperatures and it’s hard to control surface heat application. Anyone removing bottom paint should invest in a heavy-duty respirator—we’ve seen no proof that dust from sanded bottom paint is any more (or less) dangerous than the fumes released when the paints are heated. We recommend talking with your paint’s manufacturer before picking up a heat gun.