Anti-fouling: Things we should know about treating our bottoms.

Anti-fouling: Things we should know about treating our bottoms.

Fouling on boat hull

Sailors, for those of us who own boats, we understand full well the time and energy that goes in to priming, protecting and scrubbing our bottoms.

Anti-fouling is a necessity at sea but anti-foul paint is releasing millions of tonnes of microplastics and other chemicals into our waters. And as we know - microplastics and nasties in our water more often than not end up  in our food and in us.

We investigated a few anti-foul paint alternatives that focus on cleaner seas, as much as keeping our bottoms algae-free...

Since at least the ancient Egyptians, recorded accounts have referred to the variety of marine creatures that make their home on the bottom of boats. These creatures can be particularly pesky for a number of reasons including creating drag and slowing down the pace of our vessels through the water and for wooden boats, burrowing into the planking and breaking down the strength of the fine materials that separate us from the seas we sail. 

For the same amount of time, sailors and seafarers have been trying various substances and techniques to prevent weeds and barnacles from making home on our hulls. From hot wax and tar, to copper sheathing and lead cladding by the ancient Greeks, the quest for an effective biocide has taken various forms. 

Each year, our sailing and wider marine industry spends billions on coating our hulls in paint to prevent a variety of marine species from making home on boat bottoms. From pulling ships out of the water, to scrubbing off previous paint, priming and resurfacing our hulls, the process is both time-intensive and costly, whatever the size of our boat or ship.

The very nature of anti-foul techniques is to deter living species from settling on our boats, so it’s obvious that anti-foul paint is toxic, and given that anti-foul comes off our boats over time, it continues to prove pretty nasty for a variety of marine species, including coral.

We’ve found out that around 50million litres of anti-foul paint is making its way into our seas each year.


"We think  global warming alone is bleaching coral reefs, for example, but no one is talking enough about how damaging our anti-fouling paints is for coral, and how it prevents the regrowth of corals."

Dr. Rik Breur, PhD in corrosion and biofouling, founder of Finsulate


Recent research has also shown that around 20% of ALL microplastics in our seas are coming from the bottom of our boats. And with over 90% of our global marine industry using traditional toxic anti-foul, it’s pretty important that we look to clean up our act here, ASAP.

Let’s take a look at what traditional anti-foul is made of, why we need it and some innovative solutions that are helping to keep our seas cleaner AND the mussels, barnacles and algae away from our bottoms…

Why we need anti-foul

So, knowing that current anti-foul paint isn’t great for our waters, why do we bother using it at all?

Several reasons:

  1. Anti-foullng helps to keep our speed up

The earliest mention of boat fouling is attributed back to Aristotle in around 4 BC, with small fish species settling on hulls being labelled “ship-stoppers”. Whilst a very natural process for small marine species to settle on underwater surfaces, when marine species make home on the bottom of our boats and ships, they slow us down, a lot. 

  1. Anti-fouling reduces fuel consumption

When species settle on the bottom of our boats and ships, it increases drag through the water, which in turn means that engines have to work harder. This has been shown to increase our fuel usage by up to 30% and this subsequently increases the fumes and air pollution from our engines. Not great on a small boat, but a colossal impact for a 400m long cargo ship. Not great, at all.

  1. Anti-fouling protects wooden hulls from being eaten

One particularly potent marine species for wooden hulls are coral worms, that love to tunnel into wood, quickly reducing the strength and integrity of the planks that are meant to keep us separate from the sea. 



What exactly is the issue with anti-foul?

New studies estimate that around Europe alone, several thousand tonnes of paint end up in our seas each year. And, as mentioned above, most of this paint contains heavy metals and other additives which are, by design, pretty toxic to our marine environment and no doubt to us, also.

Marine coating and anti-foul paint products also contain a high level of microplastics, which are added during the manufacture process, to help bind paint together.

Studies are now showing that high volumes of the microplastic particles in marine coating specifically are being found in some of our busiest shipping lanes, getting washed off ship hulls by waves and the wind, into our seas and as the paint naturally breaks down and wears over time. These studies show that ships are leaving trails of microplastics in the water, just as planes leave vapour trails in the sky.

"There are three main reasons why anti-foul is toxic... one is that the binding materials in paint are basically plastic particles. This makes up around 20% of the plastic soup in our seas."

Dr. Rik Breur, PhD in corrosion and biofouling, founder of Finsulate


Now, remember our features on microplastics? Microplastics are so small, near impossible to clean up and are being ingested by marine animals, and even us. As a non-natural substance, these tiny pieces of plastic are being shown to have devastating impacts on our marine species, including reducing feeding activity, impacting hormone levels and even reproductive systems. Microplastics are also now already in the food we eat and the waters we drink. We need to stop more being continually added to the sea.

We spoke to Dr. Rik Breur, material scientists, winner of the European Inventor 2019 award, Doctor in anti-foul science and founder of Finsulate, on three reasons why traditional anti-foul is pretty nasty…

“There are three main reasons why anti-foul is toxic. The first is the fumes, when applying it in solvent form, the second is the binding materials in paint which are basically plastic particles. This makes up around 20% of the plastic soup in our seas. 

The third reason is really the worse part, which is the copper content, the biocides in anti-foul which keeps organisms from growing on the bottom of boats, is really damaging for our seas. We think  global warming alone is bleaching coral reefs, for example, but no one is talking enough about how damaging copper from our anti-fouling paints is for coral, and how it prevents the regrowth of corals. 

It’s a bad situation with anti-foul paints, and they make up about 90% of all anti-foul used today.”

We are seeing copper-based products being banned in places around the world, so what are our alternatives to keep our bottoms as clean as can be, and our seas, too?

Ways we limit anti-foul polluting our waters

  1. If you are still using anti-foul paint...

Anti-foul hull paint is toxic to us and our waters. The key thing is to make sure we, as Sailors, stop it getting down drains and into our water when stripping it off and re-applying it.

  • Speak to your local marina or boat yard about the facilities they have for anti-fouling and bottom painting. Many are set up with wash-down systems which catch the water coming off our hulls as we power-wash and remove last seasons cracking anti-foul.
  • Catch as much of the stuff that comes off your boat as is humanly possible: avoid working with anti-foul on a windy day and always use a tarpaulin under your boat to collect all the bits of paint and debris. The crafty Sailors amongst us have even been known use an adjusted sanding machine which is connected up to a vacuum cleaner, to collect all the removed paint! Nifty!
  • Our marinas and boatyards have information on how to dispose of this hazardous material according to local law, so give them a shout once you’ve collected the bits from your bottom for confirmation of where to put it. This is important - after taking the time to collect up this harmful paint, let’s make sure it doesn’t end up in or near our waters and that our marinas give guidance on how to properly dispose of it. What comes off the bottom of our boats is toxic!

2.  If you are switching to cleaner alternatives to anti-foul paint

Creating or finding a substance which keeps our bottoms and our seas clean isn’t such an easy task, particularly when the size of our boats on the water ranges from a few metres to several hundred.

Here are a couple of cool innovations which are great solutions to traditional anti-foul paints, with no paint. Yup, you heard us!


Alternatives to anti-foul paint

Ultrasonic anti-foul

Ultrasound anti-foul uses tiny high frequency sounds (ultrasound) to prevent species from making home on our hulls with absolutely no need for paint.

The sound is so tiny we humans can’t hear it, and given it surrounds the very close proximity to our boats, has very little impact on sonar or the ability of marine species, such as whales and dolphins, to communicate with each other - very important we protect whales and dolphins.


Ultrasonic anti-foul paint

Ultrasonic systems use a little of our boat’s battery power to work, with little negative impact on our waters and marine species AND saves us the time, energy and costs associated with pulling our boats out of the water to reapply paint every year or two.


Anti-foul film

What if we applied a sheet of film over our hulls to protect them, and replaced it only every 5 to 7 years, or so, a film containing no biocides, heavy metals or chemical compounds?

A more recent innovation in anti-fouling techniques specifically focused on keeping our seas clean and minimising collateral damage to marine life are products such as Finsulate. 

Saving the time, cost and energy of taking our boats out every year as well as keeping our seas cleaner, anti-fouls such as Finsulate cover our hulls with a film. Taking inspiration from the spines of sea urchins, the film is covered in tiny spines which prevent species being able to attach themselves to our bottoms. The process effectively reduces the hull surface area to just 5% of its total so that marine organisms such as barnacles and algae can only make home on the tiny tips of the spines. They can then be easily removed by just wiping off with a cloth. Yes, really!

Now, applying a film to the bottoms of our boats may sound like a painstaking task, with every boat being a different size and shape, but Finsulate is actually really easy to adjust and is suitable for every hull type, whether in salt or water or fresh water. Already it is being used on very small boats, all the way up to ships and is lasting up to 7 years.

Clean Sailors applying Finsulate anti-foul film

One of our crew members, Famke, spent some time with Dr. Breur in her Netherlands boatyard, applying Finsulate to the hull of her boat. Here’s Famke's quick review:

“Finsulate was super easy to apply. It’s less expensive in the long run, because it can be on the hull for 5-7 years, so you don’t have extra costs of taking your boat out of the water, scrubbing down and repainting. 

I think the only downside is that it’s not yet widely available, but then again, it is a company that still developing and growing and more and more countries are providing a team to apply the Finsulate on boats!”


Have you used ultrasonic anti-foul or Finsulate on your boats, Sailors? 

How do you find the experience?

Have you found other ocean-friendly, non-toxic anti-foul products?




Big thanks to Dr. Rik Breuer of Finsulate, for your time and expertise!