Sea-Line Thinner for Polyester Spray Filler – 1L

Sea-Line Thinner for Polyester Spray Filler is formulated to ensure the proper dilution of Sea-Line’s special polyester spray putty (filler) to achieve the correct sprayable consistency. This filler is meant to be applied with a spray gun under pressure, and it requires precise viscosity adjustment – that’s exactly what this thinner provides. By using the original Sea-Line thinner, you ensure that the polyester filler can be applied uniformly and that it retains its intended properties throughout application and curing.

When you add approximately 5–10% of Sea-Line THINNER for Polyester Spray Filler to the filler mixture, it becomes fluid enough to pass easily through a spray gun nozzle and to atomize into a fine mist. This enables the filler to fill small defects – micro pinholes, fine scratches, minor unevenness – across large surfaces like boat hulls or decks in a single, continuous application. A coat of filler sprayed with the correct dilution will dry and cure evenly, meaning it will later sand out smoothly without patches of different hardness.

It is critical to use only this specific thinner when working with the Sea-Line polyester spray filler. Using a different (inappropriate) thinner can fundamentally alter the chemical bonds in the filler material. This can lead to incomplete curing, an overly soft film, or even unwanted reactions between the filler and the solvent (such as separation or bubbling). The original thinner is composed of carefully selected organic solvents that maintain the stability of the polyester resin, ensuring that the end result – an ideally smooth, homogeneous surface – is achieved.

Usage and recommendations:

• Mixing: Prepare the filler mixture just before use. First, mix the polyester spray filler base with its catalyst hardener (benzoyl peroxide paste) according to the directions. Then gradually add the Sea-Line thinner (up to ~10% of the filler volume). Stir thoroughly until you obtain a homogeneous, slightly liquid consistency suitable for spraying.
• Spray Application: Use a spray gun with a sufficiently large nozzle (for example, 2.0–2.5 mm) intended for high-build materials. Apply 1–2 cross-coats of the thinned filler mixture. The thinner helps the filler to atomize and lay down evenly without spitting or dry patches. Each coat of filler goes on with uniform thickness, which makes subsequent leveling easier.
• Surfaces & Compatibility: The polyester spray filler (with thinner) can be applied to properly prepped surfaces: sanded and degreased fiberglass (GFK/GRP), steel and aluminum (with appropriate primer), previous polyester fillers or sound old coatings. Do not apply this mixture over self-etching (acid) primers or one-component paints, as incompatibility may cause peeling or adhesion failure. Always ensure the substrate is clean and abraded (e.g., P120-P180) for best adhesion.
• Drying & Processing Time: Thanks to proper dilution, the sprayed filler will flash off and surface-dry in roughly 30 minutes and be ready for sanding after approximately 2–3 hours (at 20°C). Once fully cured, sand the layer with appropriate sandpaper (e.g., P180-P240 grit, dry or wet) to achieve an entirely smooth surface. The thinner contributes to a consistent sanding texture across the area, without “soft” or “hard” spots. After sanding, the surface is ready for the next step (priming).