Gel Coat Application

Sea Hawk Paints Clearwater Florida

Gel Coat Preparation

Stir container thoroughly before using. Add any additives such as Sea Hawk 7125 MEK Gelcoat Thinner, Sea Hawk Patch Aid 8185, or colorants (tints) prior to catalyzing with MEKP Catalyzer (Hardener).

Please note

  • Gel Coat requires the addition of fiberglass resin hardener or catalyst (MEKP) at 1.8% by volume (77ºF)
  • Measure catalyst accurately. Under or over catalyzation may negatively affect curing, cause fading, chalking, and or improper cures. (See MEKp Catalyst Chart)
  • Gelcoat will not fully cure without the addition of a surfacing agent on the last coat, or you may over-spray with PVA before gel coal reaches its gel stage (5-10 min.)
  • Each Quart, Gallon, and 5 Gallon Pail of Sea Hawk Gel coat is sold with the appropriate amount (under ideal conditions) of MEKP catalyst and 8140 Wax Additive (Surfacing Agent) . Additional amounts are available.

Gel Coat Surfacing Agents

Sea Hawk 8140 Wax Additive: Add up to 4oz of Sea Hawk 8140 Wax Additive per gallon for tack free surface on the final coat, or if applying one coat a recommended film thickness.

Sea Hawk Patch Aid 8185: Add 25-33% Sea Hawk Patch Aid 8185 when applying gelcoat for small repairs, to improve the working properties of traditional gel coat spray patches. Patch Aid is an additive that significantly improves the application, appearance and longevity of Sea Hawk Gel Coat patches, and also gives a faster cure, harder patch, superior gloss, consistent cold weather performance, superior color match, and less halo. Patch Booster also eliminates the need to thin, or add wax to gel coats prior to patching. Do NOT combine with Sea Hawk 8140. Use either one (8140,8145) but NOT both!


Tinting: Sea Hawk Gelcoat may be tinted using Sea Hawk colorants designed for use in Sea Hawk resins and gel coats. Do not use more than 1 oz tint per quart.

Thinning Sea Hawk Gel Coat
Gel coat may be thinned up to 10% with Sea Hawk 7125 Gel Coat Thinner, or 25-33% Sea Hawk Patch Aid 8185. Use one or the other. Do Not combine. Acetone is NOT recommended except in clean up. Always add thinner, tint, or other approved additives prior to catalyzing with MEKp (also known as the hardener). Over thinning will result in an inadequate thickness for full curing. It is always best to start with 5% and work your way up to 10% if necessary.

Catalyzing Gelcoat with MEKP: The catalyst level (MEKP) should not exceed 3.0% or fall below 1.2 for proper cure. Ideal range is 1.8% @ 77°F. Gel time at 1.8% MEKP is 10-17 minutes. This time element is dependent on material temperature, room temperature, humidity, air movement, and catalyst concentration. Gelcoat should not be used when temperature conditions are below 60°F, as curing may be adversely affected.

Sanding Existing Gel Coat
The heavier fast-cut grits (40/80/100) are used to feather sand and ground out a routed area prior to filling. Use they heavier grits for the first sanding of gouges, dock dings, scratches, and blisters. You should also feather the surrounding area of the gel coat repair with 220/330. At this point, the repair is ready to prep and spray/brush with Sea Hawk Gel Coat.

Surface Preparation

Take steps to protect the rest of the surface area before starting. When working on the deck or cabin, tarp off the adjacent areas with tape, masking paper, and plastic wrap.

Gel coat over clean, dry surfaces. Remove all grease, oil, wax, or other foreign material by using Sea Hawk S-80 Wax N Grease Killer. All surfaces must be sanded. Do not apply directly over paint.

Spraying Gel Coat

Initially spray a cover coat as smooth and evenly as you can to cover your repair. This coat should be mostly in the repair area, and may be repeated. Sanding between coats is not necessary unless a surfacing agent (8140, 8185) has been added to your gel coat. Once your repair is covered, feather a ‘flow’ or sanding coat on the masked-off area making layered passes to avoid a buildup of gel coat in any one area. Each of these coats of gelcoat may involve several passes. Be even and consistent in your gun movement, overlapping each previous pass slightly and not hesitating on the ends. When spraying to a radius, flow the gel coat to the tape. In open flat areas, layer passes. Final thickness should be 18 ±2 mils minimum. As soon as you are done spraying, clean your sprayer fully with acetone. Most re-sprayed gel coat will cure in 2-4 hours, although overnight cures are ideal. Begin wet sanding with the finest grit that will remove orange peel in the re-sprayed area. This will avoid unnecessary sanding scratches. Usually 320 or 400 grit wet paper is sufficient for the initial sanding. Wet sand to a 600 finish and buff with compound and wax for shine.

Brushing Gel Coat

The major disadvantage of gel coat is that they cannot be applied in a perfect “self leveling” coat by brush. It must be mechanically finished by wet/dry sanding and polishing for a “like new” look. Sand the entire surface to be coated with 150 grit sandpaper. If cracks or gouges are present, they should be repaired first. When sanding gelcoat is completed, the surface should be free of flaws and perfectly smooth. Choose a natural bristle brush with tapered ends. Choose a shady location or an overcast day. Avoid direct sunlight. You should catalyze your material so that it cures as quickly as possible within your working time. Generally mix one-pint batches. A good practice is to pour the mixed gel coat from the mixing container into another container used for application. This further assures that no uncatalyzed material is clinging to the sides of the pot. “Lay on” the gel coat in a heavy thickness (about 10 mils) using horizontal strokes, and working from top to bottom. Avoid re-brushing as this could remove the wax additive that will rise to the top. Remember to always lap wet. Generally, one heavy coat is sufficient. However, if you have opacity problems two coats may be necessary with a light sanding between coats. Once the coating (gelcoat) has cured, it should be block sanded using a 250 wet grit paper to remove all brush marks and high spots. Following this, it should be wet sanded with 320,400, and 600 wet grit paper, buffed, polished and waxed.

Important Tips

1. Clean repair area and all tools with acetone prior to application.

2. Pot life (amount of time for application of the product) shortens dramatically as you mix larger batch sizes. Keep in mind that you have a limited time to apply what you have mixed (usually between 5-15 minutes).

3. Measure catalyst accurately. Under- or over-catalyzed gel coat will cure slower and look faded or chalky.

4. Do not add more than 10% by volume Sea Hawk 7125 Gel Coat Thinner or 25-33% Sea Hawk Patch Aid 8185. Do Not Combine!

5. Gel coat will not fully cure without adding a surfacing agent or over spraying with PVA.

6. Do not work in direct sunlight.

7. Check color thoroughly before applying. Gelcoat will not generally darken or change colors when it dries.

8. Store gel coat in a cool, dry place to preserve shelf life.

9. Gel coat should be applied in temperatures of 60ºF to 80ºF.

10. Always use eye and hand protection.

11. Read all warnings on product labels, product technical data sheets, and Material Data Safety Sheets.

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