Marine Paint Thinners – How to Ensure Compatibility Between Your Paint and Thinner

Thinners are a very important part of your boat re-painting process. Some new boat painters are very intimidated by the idea of using thinners. In the marine paint industry, some thinners have a bad reputation for ruining paint jobs or being too harsh on the boat substrate. Unfortunately, as much as we wish we could blame the thinner, usually it is “user error” that causes the most grief when using thinners.

Thinners are powerful substances that break the bonds in paint between the bonding agent and pigment. Marine paint is oil-based, and so it has a bad habit of becoming thicker over time and losing its leveling properties. This means that the paint will not lay flat, and this causes paintbrush marks and uneven coverage of your boat. Uneven coverage is the most dangerous consequence of not using thinners. Water can penetrate uneven areas and cause considerable hull damage.

Thinners are also known as “conditioners” because they condition the oil paint to flow smoothly, have even leveling, and uniform drying time. When using marine paint, water is NOT a thinner option. In fact, using water will cause a chemical reaction that will make the paint separate and become unusable. You must use marine paint thinners designed for oil-based paints.

The first key to using the right thinner is to find out what brand of marine paint you are using. The most ideal action to take is to consult the brand about which thinner to use. Most of the time, the thinner that’s compatible with your paint will be listed on their website or be available by calling their customer service number.

Marine Paint Thinners

Marine Paint Thinners

The second key to using the right thinner is to consider if your paint has antifouling properties. Paint with antifouling needs to be thinned with a thinner that’s compatible with antifouling paints. Most brands will have their own thinner for antifouling paints. If you are using typical marine paint, then most brands thinners will be called something like an “epoxy” thinner.

The third secret to using thinners is to carefully follow the directions on the when to use the thinner and how much to use. Most brands will call to add 10% to 15% thinning solution to paint on windy days or warm days. This means you add 10% of the total volume of paint in thinner. If you are using 10 ounces of paint, you would add 1 ounce of thinner and mix in with the paint. Using thinner on warm days ensures you have even coverage and your paint won’t dry before you’re done with the total coat.

If you find that you’ve added the wrong thinner, the best thing to do is to throw the can of paint away and start over. Applying paint with the wrong thinner can ruin the primer and even your boat’s substrate if it’s not compatible. It’s better to be safe than sorry. After all, you’ve already put so much work into surface preparation and priming, why risk ruining the whole job?

Share Your Comments