When spraying gelcoat with a preval sprayer, strain your gelcoat after it has been reduced and activated using a paper disposable strainer then disregard the plastic strainer attached to the straw from the preval sprayer. This will give you a heavier and more consistent spray.
For over-all gelcoat refinishing use the same mix and steps as shown in the instructional instead of a preval sprayer, apply using an automotive spray gun, (no special tip needed). Gelcoat has to be thinned the same for a suction feed or gravity feed spray gun although using a gravity feed spray gun will leave more orange peel than necessary.
To apply using a suction feed spray gun will give you a smoother surface as gelcoat is more atomized throwing a finer spray yet releasing most solvents when spraying with around 60lb psi with in line water separator, keep your spray gun moving to avoid a wrinkle in the gelcoat over lapping each coat. The heavier the coat is applied the more micro pin holes will exist, using a suction feed spray gun will give you a better quality finish.
Never spray gelcoat in direct sunlight during a hot day, the surface will skin too fast trapping solvents creating pin holes leaving a dull finish at job completion.
Spraying gelcoat on the entire boat deck or hull be sure to prime first to cover all pin holes and repaired areas also to avoid blistering especially near the waterline, apply 4 coats at waterline and below, remember you will be sanding off at least a coat leaving you with 3 coats needed for a water bearier, 2 coats are fine for the rest of the vessel. Use Duratech vinylester primer some recommend polyester primer though it may be too brittle and eventually the primer may chalk beneath the sprayed gelcoat and chip or flake off easily. using auto primers for a gelcoat refinish is a bad idea, spray at least 5 coats of gelcoat when re-surfacing a complete boat deck or hull.
For gelcoat spot repair be sure to sand far past the repaired area to be sprayed to make sure your gelcoat spray does not exceed over the unsanded surface, use the proper grit for sanding during the final prep.
To avoid a wave or warped finish at job completion, never use tape around the area, it may only create a step as overspray build up exceeds onto the tape. Let your polisher remove any fine overspray that traveled onto the unsanded gelcoat if any, if using tape or masking paper stay clear of the area to be sprayed at least a couple feet.
Spraying true colors, red, blue, green etc. and your color is a bit off give a bigger blend line and spray 3 coats of clear gelcoat over the base color and 1 to 2 ft each side of your color blend.
Let your gelcoat cure for at least 48 hours before sanding that will give you a better blend after polishing as the blend line will be much harder and thinner without breaking away leaving a gelcoat repaired area invisible at all angles, using the proper gelcoat additives of course.
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