Most paint failures have nothing to do with the paint itself. Fisheyes, blushing, poor adhesion, runs and peeling usually come down to contamination, weather or rushed preparation. Fortified Oceanic in Newport, Sydney helps boat owners and professional painters across Australia get it right the first time. This guide covers what to control before and during a paint job so the finish lasts.
1. Contamination: the number one cause of failure
Paint can only stick to a clean surface. The most common contaminants on boats are wax, silicone, salt, oil, grease, fingerprints and sanding dust.
Silicone and wax cause fisheyes, small craters where the paint pulls away. They come from polishes, boat waxes, silicone sealants and even some sprays used nearby. Remove them before sanding, or the sandpaper will just spread them deeper into the surface. Use a dedicated solvent cleaner such as Awlgrip Awlprep, Altex D30 Degreaser/Dewaxer or Wax and Grease Remover, wiping on with one clean cloth and off with another before it dries.
Salt is invisible but draws moisture through the paint and causes blistering. Wash the boat thoroughly with fresh water and let it dry completely before you start. Altex P40 Pre-Painting Cleaner is a good water-based option.
Dust ruins a gloss finish. Wipe down with a Gerson Tack Cloth or 3M Aqua Tack Cloth just before each coat, and wet down the ground around the boat to keep dust from lifting.
Hands and gloves: skin oils and hand creams leave marks paint won't cover. Wear clean nitrile gloves when handling a prepared surface.
2. Surface preparation
Sand to the grit the data sheet recommends. Too fine and the paint has nothing to grip; too coarse and the scratches show through. Use quality discs like KOVAX Maxcut Super Tack Discs and get into tight spots with a Scotch-Brite hand pad. Feather all edges, fill and fair any damage, and make sure fillers and primers are fully cured before you sand them.
Moisture in the hull: painting over damp fibreglass or timber traps water and leads to blistering and peeling. Let the hull dry out properly after haul-out, especially below the waterline.
Amine blush: some epoxies form a waxy film as they cure, especially in cool, damp weather. Wash it off with water and a Scotch-Brite pad before sanding or overcoating.
3. Temperature
Every paint has a minimum and maximum application temperature on its data sheet. Too cold and the paint cures slowly or not at all, stays soft, and may never reach full hardness. Too hot and it dries too fast, causing dry spray, poor flow, brush marks and solvent pop. Remember it's the surface temperature that matters, not just the air. A hull sitting in full sun can be far hotter than the air, and a steel or aluminium hull can be much colder first thing in the morning.
4. Humidity and dew point
High humidity is one of the biggest causes of failure in coastal Australia. Moisture can cause blushing (a cloudy, milky finish), loss of gloss and poor adhesion between coats. A good rule is to keep the surface temperature at least 3°C above the dew point, and to check the data sheet for the maximum humidity allowed.
Watch out for dew. As the sun goes down, the temperature drops and moisture settles on the surface. Stop painting early enough in the afternoon that the coat can set before dew forms. Don't start in the morning until the surface is completely dry.
5. Wind, sun and weather
Wind blows dust, insects and debris onto wet paint, speeds up drying so the paint can't flow out, and carries overspray onto neighbouring boats. Tent or screen the work area, and don't spray on windy days.
Direct sun heats the surface and flashes off solvent too quickly. Work in the shade, or follow the shade around the boat.
Rain and spray on uncured paint will spoil the finish. Check the forecast for the full cure time, not just the day you're painting.
6. Mixing and application mistakes
Use the exact mixing ratio from the data sheet and measure accurately. Respect the induction time and pot life, and never use paint past its pot life. Use the correct thinner and only as much as allowed. Strain paint through a CAM ultra-fine paint strainer before it goes in the gun. If you're spraying, drain water and oil from your compressor and air lines, since they're a common hidden source of fisheyes.
Overcoat windows: apply the next coat inside the time window on the data sheet. Too soon traps solvent and causes wrinkling or soft paint. Too late and the next coat may not bond without sanding.
Film thickness: heavy coats cause runs, sags and solvent entrapment. Several thin coats are better than one thick one.
7. Pre-paint checklist
Before you open the tin, ask yourself: is the surface clean, dry and free of wax, silicone and salt? Is it sanded to the right grit and dust-free? Are the air and surface temperatures within range, and is the surface at least 3°C above dew point? Is the wind low and the area screened? Is the work masked properly with 3M 233+ masking tape? Do you have enough time to finish before dew or rain?
Always follow the manufacturer's technical and safety data sheets. Having trouble with a paint job, or want help planning one? Contact the Fortified Oceanic team in Newport for advice and trade pricing.