How To: Soda Blast your Boat

You have a thick layer of antifouling paint on the bottom of your boat. It’s rough and worn around the edges, so you’d like to get rid of it and have a nice smooth bottom that will help you sail faster. The options are quite simple.
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You have a thick layer of antifouling paint on the bottom of your boat. It’s rough and worn around the edges, so you’d like to get rid of it and have a nice smooth bottom that will help you sail faster. The options are quite simple. You can put on a Tyvek suit and respirator and manhandle a random orbit sander for a week (or hire someone to do it for you), or you can call John Armstrong at Salty Dawg Boatworks in Narragansett, Rhode Island, and have his people soda blast the bottom of your boat. Armstrong and his crew cover the entire New England coast, from New Jersey to Maine. He says he spent most of this past summer in Maine working for Front Street boatyard Lyman-Morse and other well-known yards.

The “soda” in soda blasting is sodium bicarbonate, which is similar to the baking soda you buy for cooking at home, but crystallized so it can be used in the rain. It can also be used with a water jet instead of an air compressor, although Armstrong says that when he blasts this way he ends up walking around in a three-inch-deep pile of wet sludge. “I’ll never do it that way again,” he admitted in a recent conversation.

Because the soda breaks upon impact into micro-fragments, it doesn’t damage substrate the way sand blasting can. All it does is peel off the paint. Soda blasting can also be done on cars, masonry and rusted metal parts. The one situation in which Armstrong says soda blasting is not a good idea is on a boat that was built with either a very thin gelcoat or where the gelcoat has been sanded away to almost nothing. In these cases, he recommends the hull be sanded rather than blasted so as not to risk damage to the underlying fiberglass laminate.

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A soda blaster needs a compressor, a supply of soda and a blasting gun. You can purchase simple soda-blasting kits for a few hundred dollars (Harbor Freight has one for $99), but you will need to clean up both the excess soda and the paint chips afterward, so you are probably better off hiring an expert. Should you decide to try it on your own, a face mask is essential.

A professional blaster will roll in with a large truck, completely mask off the boat and the area beneath it, and then set to work. According to Armstrong, it takes about a day to set up the containment area for an average boat. “The soda blasting goes really quickly, once we have everything set up,” he says. “For most boats, the entire process takes one to two days and most of that time is the setup.”

Soda blasting quickly removes old paint without damaging the gelcoat underneath

Soda blasting quickly removes old paint without damaging the gelcoat underneath

Armstrong recommends that the hull also is lightly sanded after blasting to remove any remaining soda residue or paint that might have been only partially blasted off. “Most yards spend a couple of hours sanding before they apply the epoxy barrier coat,” he says, adding that the sanding makes it easier for the epoxy to adhere and ensures that the bottom is completely clean.

How much does it cost? According to Armstrong, the price varies depending on the length of the vessel. For example, a 30-foot boat might be around $45 per foot, while a 100-foot boat would be around $130 per foot because of the increased beam. “Our average job works out around $35 to $45 per foot,” he says.

As soon as the hull has been properly sanded, it is time to apply the barrier coat. In most cases, this will be an epoxy-based paint that has to be applied smoothly and quickly. Most products take three or four coats to build up an impermeable layer. In fact, the majority of paint manufacturers recommend measuring the thickness of the barrier coat to ensure there is no chance water can penetrate.

When the barrier coat has dried and hardened, you can apply bottom paint in the color of your choice. Then you can launch and go sailing, safe in the knowledge that your boat is protected in the best way possible.

Photos by Roger Marshall

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