(787) 761-4810

Gelcoat application · 7 steps

On a surface

Gelcoat goes on last. The exposed surface needs an approved curing method: usually wax in the final coat or an approved external barrier.

Gelcoat being sprayed onto a repaired fiberglass surface.

  1. Step 1. Inspect the substrate

    Check that the laminate is sound and repairs are complete. Confirm compatibility of the resin, fillers and any primer underneath.

    Identify the substrate and its condition

    Confirm compatibility and the extent of damage before proceeding. A surface finish does not replace a structural repair.

  2. Step 2. Clean and sand

    Remove wax and contamination before sanding. Prepare the surface and remove dust according to the finish instructions.

    Wipe clean first

    Sand the clean surface

    Remove dust

    Remove wax and contamination before sanding. Use the specified repair profile, abrasive and final cleaning method.

  3. Step 3. Prepare the gelcoat

    Prepare for the permitted brush, roller or spray method. If tinting, use approved pigment within its limits, blend before MEKP and validate a separate cured sample. Catalyze a manageable amount using the specified ratio and measurement basis. Do not add unapproved solvents.

    Tinting your gelcoat? See how to color polyester gelcoat

    MEKP last, when ready to apply

    Mix and use within working time

    Use the actual gelcoat instructions for catalyst type, amount, measurement basis and conditions. The illustrated color is not a pigment recipe.

  4. Step 4. Apply the coats

    Apply and measure the specified thickness. If the process needs multiple coats, observe the interval between coats and keep intermediate coats unwaxed where required.

    Apply evenly

    Verify the specified thickness

    Use the permitted application method and measure the specified wet-film thickness. Observe coat intervals; this diagram is not to scale.

  5. Step 5. Prepare the final surface cure

    Use the specified system for the last coat: pre-waxed gelcoat, an approved wax additive or an approved external barrier such as PVA.

    Specified wax system

    Or an approved external barrier

    Use the approved option for the final exposed surface, not both by default. Do not add extra wax to pre-waxed material unless specified; wax does not replace MEKP.

  6. Step 6. Allow to cure and remove residue

    Wait for the required cure. Remove wax or PVA using its specified procedure before sanding or finishing the surface.

    Allow the required cure

    Remove residue before finishing

    After the required cure, remove wax, barrier residue or contamination using the specified method before sanding or coating.

  7. Step 7. Finish and inspect

    Sand and polish if the finish requires it, without cutting through the gelcoat. Inspect the result and observe the required cure before putting the part into service.

    Finish only when ready

    Inspect before use

    Use the approved surface-cure method first, then remove residue and finish as specified. Check cure, color and coverage; appearance alone does not prove full cure.