Solvents & Thinners

Solvents and thinners are the unsung workhorses of boat and RV maintenance. They adjust the viscosity of paints and varnishes so coatings flow, level and cure properly, and they dissolve residues that would otherwise ruin a finish. Whether you are refinishing brightwork, repainting topsides, or prepping fiberglass for repair, choosing the right solvent can make the difference between a glass-smooth result and a streaky, blistered one.

What Solvents and Thinners Do

A thinner is added to a coating to reduce its thickness for brushing, rolling or spraying. A solvent is typically used for cleaning, degreasing, wiping down surfaces before painting, and flushing brushes and tools. Some products do both, but they are not interchangeable across every coating system. Thinners are generally formulated to match a specific paint chemistry, such as one-part enamels, two-part polyurethanes or epoxies, so using the wrong one can affect curing, gloss and adhesion.

Key Considerations When Choosing

• Coating compatibility: Always match the thinner to the paint or varnish system. Manufacturers specify which thinner suits their one-part, two-part and epoxy products.
• Evaporation rate: Slower thinners help maintain a wet edge on hot, windy days and aid rolling and tipping. Faster-evaporating formulas are common for spray applications and general cleaning.
• Application method: Brushing, rolling and spraying often call for different thinners, so check whether a product is labeled for the method you plan to use.
• Odor and regulations: Low-odor and compliant formulas can be more comfortable in enclosed spaces such as a cabin or bilge, and some regions limit volatile organic compounds.
• Safety: These products are flammable and should be used with good ventilation, appropriate gloves and eye protection, and stored in tightly closed containers away from heat.

Top Brands in Solvents & Thinners

Epifanes is a respected name in yacht coatings, and its thinners are engineered to pair with its varnishes and paints. Its brush thinner is described as double distilled for purity and is intended for brushing or rolling most one-component primers, paints and varnishes, while separate formulas exist for polyurethane and epoxy systems.

Pettit Paint offers a long-standing marine line, and its 120 Brushing Thinner is a general-purpose option for thinning solvent-based topside enamels and varnishes. It evaporates at a moderate rate and is also the recommended thinner for cleanup of those products and most Pettit antifouling paints.

Klean-Strip is a familiar name in shop and workshop solvents, with products such as acetone and odorless mineral spirits. Acetone is useful for thinning fiberglass resins and epoxy and for cleaning residue, and it dries fast without leaving residue. The odorless mineral spirits are a highly refined, low-odor choice for cleaning brushes, tools and equipment.

Spray 9 rounds out the selection with a cleaning-focused product that suits general maintenance and residue removal around the boat, RV or garage.

Getting the Best Results

Add thinner gradually and mix thoroughly, staying within the manufacturer's recommended ratio, since over-thinning can weaken coverage and film build. Wipe surfaces with a clean solvent-dampened rag before painting to remove sanding dust and contamination, and clean brushes promptly after use so coatings do not harden in the bristles. Dispose of used solvents and soaked rags according to local regulations.