Paint & Varnish Thinners and Solvents FAQs

What Do You Use Marine Paint Solvents For?

Solvents play an important role in boat painting projects. First, wiping down surfaces to be painted surfaces with the appropriate solvent to remove dirt and residue promotes better paint adhesion.

While you paint, certain solvents may be used to improve paint flow and make it easier to maintain a wet or working edge. Manufacturers often recommend a specific solvent/thinner for use with 1-part paints and 2-part paints and epoxy-based finishes.

If you accidentally get paint somewhere it should not be, various solvents may be used to clean up the excess paint. When you have completed the job, clean your brushes, rollers, spray guns, and other equipment with the same solvent.

Do You Need to Thin Marine Paint?

Getting the right marine paint viscosity is key to getting the best result. If the paint is too thick, roll and tip work will be difficult, and spraying will be almost impossible. If the paint is too thin, you will find it tough to keep a wet edge.

To get the right consistency, use an appropriate amount of thinner designed for the ambient temperature and specific application. In hot weather, for example, some paints may be thinned up to 5 percent with mineral spirits. The resulting paint viscosity will better enable you to maintain a wet edge.

Its also common to thin other coatings like marine varnish. For example, users often thin their first coats of varnish up to 50 percent for easier application and better penetration.

How Do You Thin Marine Paint?

1. When thinning marine paint, read the manufacturers paint container label. Ensure that you have more paint than thinner in the mix, as that is the best way to avoid too-thin paint that is not true to color. Note that each kind of paint and application method requires a specific consistency and painting technique. For reference, consider that most paint systems call for no more than 5% to 10% of thinner.


2. Measure out the correct paint amount, and pour it into a mixing bucket. Add the proper amount of thinner, at little at a time, as you use a paint stirrer. Keep checking until you get the right consistency.


3. Apply two coats of the paint/thinner blend on your paintable surface, and judge the finished result. Look for runs and drips, and ensure that the paint completely covers the test surface. If the paint is excessively thick, apply a little thinner and reapply the mixture. If the paint is too thin, add some more un-thinned paint until the viscosity is right.

How Do You Use Solvents to Prep for Painting?

Solvents are widely used painting prep tools. Use them to clean paintable surfaces prior to applying primer or paint. Solvents such as mineral spirits can effectively function as a paint thinner for enamel paints and varnish.

Use a dewaxer-type solvent to wipe down fiberglass and other surfaces prior to painting. These solvents effectively remove wax, grease, oil, dirt, and other contaminants that could negatively impact the quality of the paint job.

After you have finished painting, grab some mineral spirits and clean your paint-splattered tools. Brush cleaner is a milder, water-rinsable solvent that is ideal for removing paint, varnish, and shellac from nylon and natural-bristle brushes.

What is a Dewaxer?

A dewaxer and surface preparation solvent wash efficiently cleans paintable surfaces. The dewaxer also removes surface contaminants that could affect adhesion. Contaminants include wax, grease, oil, and mold release agents.

As a result, certain primers, paints, and adhesives will demonstrate better adherence and will last longer. This solvent also effectively cleans painting tools and equipment.

What is Brushing Reducer?

A brushing reducer is a slowly evaporating solvent designed for use in certain epoxy products and 2-part polyurethane products. As the solvent evaporates, it keeps the paint film open and maximizes the paint flow. At the same time, the reducer helps to minimize undesirable brush marks and roller stipple. As with any solvent, read the manufacturers directions to determine the amount to be added.

How Do You Use Reducer Solvents with Paint or Varnish?

Generally speaking, reducer solvents help paint or varnish to cure (or set up) faster or slower, taking the ambient air temperature into account. For example, a hot weather reducer causes paint or varnish to dry more slowly in hot temperatures. In contrast, a cool weather reducer spurs paint or varnish to cure more quickly.

What Is the Difference Between a Brushing Reducer and Spray Reducer?

A brushing reducer and spray reducer are each tailored to the specific application method. The brushing reducer allows paint to slow down its evaporation time. So, the paint film stays open, and optimizes flow and leveling. At the same time, roller stipple and brush marks are minimized.

In contrast, a spray reducer is a valuable spraying application tool. Adding the reducer enables the paint to dry much faster than usual. Spray reducers are generally formulated for use with 2-part polyurethane topside paint systems.

Do You Need to Use a Spray Reducer in Order to Spray Marine Paint?

Yes, you will definitely need a spray reducer to properly spray marine paint. The reducer helps to maximize the spraying efficiency, or atomization, of the paint. The reducer evaporates quickly, which enables the solvent to leave the paint film before the paint develops a skin. Slow reducers are designed for use in warmer weather, while fast reducers are geared for use in cooler conditions.

What Are the Most Common Solvents Used with Marine Paints and Varnish?

Marine solvents are integral components of many boat painting projects. Always follow the manufacturers instructions, and use proper personal protective equipment where necessary.

Mineral Spirits are an all-purpose solvent particularly useful for thinning oleoresinous paint, enamel, and varnish. Also great for cleaning tools.

Linseed oil is available in raw or boiled form. Raw linseed oil helps wood retain moisture to prevent checking, cracking, and shrinking. Boiled linseed oil can be added to oil-based paints to speed film drying and hardness.

Acetone is a strong solvent good for dissolving two-part epoxy before it sets up, for thinning resins, and cleaning fiberglass repair tools. Serious stuff!

Denatured Alcohol is great for use with shellac, but will not thin most other coatings. Campers and others have sworn by it for years for use in alcohol stoves. Denatured alcohol is not potable. The term denatured means it is poisonous and dangerous!

Toluol is a toluene-based solvent for certain oil paints, lacquers, and adhesives. Paint chemists often use this solvent.

Brush Cleaner is a milder, water-rinsable solvent. It removes paint, shellac, varnish, etc. from natural and nylon paint brushes.